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• Managing multiple Apache proxies simultaneously (mod_proxy_balancer)

  - by Hank

  The frontend of my web application is formed by currently two Apache reverse proxies, using mod_proxy_balancer to distribute traffic over a number of backend application servers. Both frontend reverse proxies, running on separate hosts, are accessible from the internet. DNS round robin distributes traffic over both. In the future, the number of reverse proxies is likely to grow, since the webapplication is very bandwidth-heavy. My question is: how do I keep the state of both reverse balancers / proxies in sync? For example, for maintenance purposes, I might want to reduce the load on one of the backend appservers. Currently I can do that by accessing the Balancer-Manager web form on each proxy, and change the distribution rules. But I have to do that on each proxy manually and make sure I enter the same stuff. Is it possible to "link" multiple instances of mod_proxy_balancer? Or is there a tool out there that connects to a number of instances, and updates all with the same information? Update: The tool should retrieve the runtime status and make runtime changes, just like the existing Balancer-Manager, only for a number of proxies - not just for one. Modification of configuration files is not what I'm interested in (as there are plenty tools for that).

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• /dev/input/uinput Device appears to be 'broken'

  - by Adam Luchjenbroers

  I'm trying to setup Pystromo so that I can remap the keys on my Belkin N52TE gamepad. Pystromo basically captures the key strokes and then outputs the remapped keystrokes to the uinput device. However, at the moment it simply swallows the input and outputs absolutely nothing. I've tracked the issue to something being wrong with my uinput device, with the smoking gun being: # ls -l /dev/input/uinput crw-rw---- 1 root plugdev 10, 223 Dec 31 2009 /dev/input/uinput # cat /dev/input/uinput cat: /dev/input/uinput: No such device The uinput module is loaded, and can be clearly seen via lsmod. Anyone seen this before, or can think of something worth attempting? Current Setup Gentoo Linux Kernel 2.6.32 (Gentoo Sources 2.6.32-r1) HP DV7 Laptop Output dmesg dmesg | grep uinput does nothing, and no new lines appear if I run modprobe -r uinput && modprobe uinput. Yet the uinput module can clearly be seen when running lsmod: # lsmod | grep uinput uinput 6200 0 lsusb # lsusb Bus 005 Device 003: ID 050d:0200 Belkin Components Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 004 Device 002: ID 1532:0101 Razer USA, Ltd Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 002 Device 002: ID 5986:0143 Acer, Inc Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 007 Device 002: ID 03f0:171d Hewlett-Packard Wireless (Bluetooth + WLAN) Interface [Integrated Module] Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub lsusb -v PasteBin Update Hmm, updating evdev and hal seems to have partially fixed it. /dev/input/uinput still can't be accessed but Pystromo is now remapping keys successfully. I'm a little bit mystified about what's going on here, but it seems that my understanding of how all this works is flawed. Since I've posted a bounty, I'll leave this here for someone to post an explanation for how user-space input devices work under the hood.

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• Can I take my ReadyNAS drive in Raid1 and plug it straight into new different machine?

  - by jacko

  I would assume that I can just take my HDD out of my NAS (in raid1 mirror) and plug it into another enclosure and have it work off the bat but I'd like to make sure... Any ideas? Edit: My current setup is a Netgear ReadyNAS in (hardware) raid1. I'm hoping to replace this with a home theatre type PC (possibly running Ubuntu), and would like to migrate my data without having to do a bulk transfer over my network between the 2 machines. Can anyone confirm the case for the Netgear ReadyNAS? Edit: Ok after further reading it seems that the ReadyNAS Duo formats my drive as ext3 in 16k blocks. There are instructions for mounting a drive into a linux box here: Mounting Sparc-based ReadyNAS Drives in x86-based Linux There is also talk about a linux image here: ReadyNAS Data Recovery - VMware recovery tool I'm not sure whether this means they ReadyNAS actually implements software raid under the hood, or what? So it appears like it IS do-able, but do any of you linux guru's know whether this is viable and whether the fact that they are in raid 1 affect matters?

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• Google Chrome doesn't want to access Facebook

  - by Pieter van Niekerk

  I have been experiencing a bit of a problem with Chrome over the last couple of days where it doesn't want to access Facebook. When I open Chrome it works fine for a while and then if I were to refresh the page it would give me the Chrome 'This webpage is not available' message. This webpage is not available Google Chrome could not load the webpage because www.facebook.com took too long to respond. The website may be down, or you may be experiencing issues with your Internet connection. Here are some suggestions: Reload this webpage later. Check your Internet connection. Restart any router, modem, or other network devices you may be using. Add Google Chrome as a permitted program in your firewall's or antivirus software's settings. If it is already a permitted program, try deleting it from the list of permitted programs and adding it again. If you use a proxy server, check your proxy settings or contact your network administrator to make sure the proxy server is working. If you don't believe you should be using a proxy server, adjust your proxy settings: Go to the wrench menu Options Under the Hood Change proxy settings... LAN Settings and deselect the "Use a proxy server for your LAN" checkbox. This problem only persists when using the proxy and doesn't occur at all when not on the proxy. I have also tried different browsers (IE9 and Firefox 9.01) but it doesn't occur in any of them. This problem goes away for a while when I restart Chrome, only to happen again a couple of minutes later. I have tried deleting the cookies for Facebook without restarting Chrome, but to no avail. I am using Windows7 with Chrome 17

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• How many reverse proxies (nginx, haproxy) is too many?

  - by Alysum

  I'm setting up a HA (high availability) cluster using nginx, haproxy & apache. I've been reading great things about nginx and haproxy. People tend to choose one or the other but I like both. Haproxy is more flexible for load balancing than nginx's simple round robin (even with the upstream-fair patch). But I'd like to keep nginx for redirecting non-https to https among other things right at the point of entry to the cluster. On the other hand, nginx is a lot faster for serving static contents and would reduce the load on the powerful apache which loves to eat a lot of RAM! Here is my planned setup: Load balancer: nginx listens on port 80/443 and proxy_forwards to haproxy on 8080 on the same server to load balance between the multiple nodes. Nodes: nginx on the node listens to requests coming from haproxy on 8080, if the content is static, serve it. But if it's a backend script (in my case PHP), proxy forward to apache2 on the same node server listenning on a different port number. Technically this setup works but my concerns are whether having the requests going through several proxies is going to slow down requests? Most of the requests will be PHP requests as the backends are services (which means groing from nginx - haproxy - nginx - apache). Thoughts? Cheers

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• Can a pool of memcache daemons be used to share sessions more efficiently?

  - by Tom

  We are moving from a 1 webserver setup to a two webserver setup and I need to start sharing PHP sessions between the two load balanced machines. We already have memcached installed (and started) and so I was pleasantly surprized that I could accomplish sharing sessions between the new servers by changing only 3 lines in the php.ini file (the session.save_handler and session.save_path): I replaced: session.save_handler = files with: session.save_handler = memcache Then on the master webserver I set the session.save_path to point to localhost: session.save_path="tcp://localhost:11211" and on the slave webserver I set the session.save_path to point to the master: session.save_path="tcp://192.168.0.1:11211" Job done, I tested it and it works. But... Obviously using memcache means the sessions are in RAM and will be lost if a machine is rebooted or the memcache daemon crashes - I'm a little concerned by this but I am a bit more worried about the network traffic between the two webservers (especially as we scale up) because whenever someone is load balanced to the slave webserver their sessions will be fetched across the network from the master webserver. I was wondering if I could define two save_paths so the machines look in their own session storage before using the network. For example: Master: session.save_path="tcp://localhost:11211, tcp://192.168.0.2:11211" Slave: session.save_path="tcp://localhost:11211, tcp://192.168.0.1:11211" Would this successfully share sessions across the servers AND help performance? i.e save network traffic 50% of the time. Or is this technique only for failovers (e.g. when one memcache daemon is unreachable)? Note: I'm not really asking specifically about memcache replication - more about whether the PHP memcache client can peak inside each memcache daemon in a pool, return a session if it finds one and only create a new session if it doesn't find one in all the stores. As I'm writing this I'm thinking I'm asking a bit much from PHP, lol... Assume: no sticky-sessions, round-robin load balancing, LAMP servers.

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• What's the piece of hardware listening on Facebook's or Wikipedia's IP address?

  - by Igor Ostrovsky

  I am trying to understand how massive sites like Facebook or Wikipedia work, for my intellectual curiosity. I read about various techniques for building scalable sites, but I am still puzzled about one particular detail. The part that confuses me is that ultimately, the DNS will map the entire domain to a single IP address, or a handful of IP addresses in the case of round-robin DNS. For example, wikipedia.org has only one type-A DNS record. So, people from all over the world visiting Wikipedia have to send a request to the one IP address specified in DNS. What is the piece of hardware that listens on the IP address for a massive site, and how can it possibly handle all the load coming from the requests for users all over the world? Edit 1: Thanks for all the responses! Anycast seems like a feasible answer... Does anyone know of a way to check whether a particular IP address is anycast-routed, so that I could verify that this really is the trick used in practice by large sites? Edit 2: After more reading on the topic, it appears that anycast is not typically used for dynamic web content. Anycast is usually used for UDP (e.g., DNS lookups), or sometimes for static content. One interesting thing to note is that Facebook uses profile.ak.fbcdn.net to host static content like style sheets and javascript libraries. Each time I ping this name, I get a response from a different IP address. However, I can't tell whether this is anycast in action, or a completely different technique. Back to my original question: as far as I can tell, even a large site will have a single expensive piece of load-balancing hardware listening on its handful of public IP addresses.

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• What's the best way to run Drupal and Django sites behind the same Varnish server?

  - by Alexis Bellido

  I have a high traffic website running with Drupal and Apache, five web servers behind a Varnish server load balancing. Let's say this site is example.com. I'm using five backends and a director like this in my default.vcl: director balancer round-robin { { .backend = web1; } { .backend = web2; } { .backend = web3; } { .backend = web4; } { .backend = web5; } } Now I'm working on a new Django project that will be a new section of this site running on example.com/new-section. After checking the documentation I found I can do something like this: sub vcl_recv { if (req.url ~ "^/new-section/") { set req.backend = newbackend; } else { set req.backend = default; } } That is, using a different backend for a subdirectory /new-section under the same domain. My question is, how do I make something like this work with my director and load balancing setup? I'm probably going to run two or more web servers (backends) with my new Django project, each one with a mix of Gunicorn, Nginx, and a few Python packages, and would like to put all of those in their own Varnish director to load balance. Is it possible to do use the above approach to decide which director to use?, like this: sub vcl_recv { if (req.url ~ "^/new-section/") { set req.director = newdirector; } else { set req.director = balancer; } } All suggestions welcome. Thanks!

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• Insufficient channel capacity of 1GBit

  - by Roman S

  There is a Caching Server (Varnish): it receives data from Amazon S3 on request, saves it for some time and gives it to the client. We have encountered the problem of insufficient channel capacity of 1GBit. Peak load within 4 hours completely chokes the channel. Server performance is sufficient for now. Approximately 4.5TB of data are transmitted per day. More than 100TB are accumulated per month. The first thought that comes to mind is simply to add one more 1GBit port and sleep peacefully until 2GBit are not enough (it may happen quite quickly) or one server is not able to handle it. And then we just need to add new Caching Servers. But now we need a Load Balancer, which will send requests on one and the same URL, always on one and the same server (to avoid multiple copies of the same cached objects). Here are the questions: Does a Balancer need a band equal to sum of all bands of Caching Servers? What shall we do in case there are no ports in a Balancer? Should we add more Balancers or solve the problem by means of Round robin DNS? What are the standard approaches to such problems? Can anyone advise hosting-companies, which can solve this problem? We are interested in American and European markets.

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• HyperV - low CPU usage

  - by Klark

  I am very new to HyperV and virtual machine philosophy in general, so please expect more or less nooby questions :) I have a server that is only used as a host for virtual machines. OS is windows server 2008 R2 and it is running on 16 CPU and 48 GBs of RAM. On aforementioned server there are 8 VMs, each having 4 CPUs and 4 GBs of RAM. On those VMs we are running some CPU intensive tasks. Each machine has nearly 100% cpu usage. After I noticed slow performance I went to the host machine and started playing with process explorer. It turned out that cpu usage is very low. Also I/O is very low, and of course, memory consumption is high, which is expected. Of course, I don't expect that those 4 virtual cores dedicated to a VM work as fast as real, hardware 4 cores, but still I expected a higher consumption of real hardware. Is this sort of behaviour normal? I see that the most of CPU usage on host machine are marked as interrupts (which I guess is normal) and all those interrupts are passed to only one core (which is strange). Are there out of box optimization that I could perform to finally use all that processing power that is under the hood. My knowledge of virtualization technology is near to embarrassing, so I would be grateful for any links that could enlightened me :) Thanks.

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• Use subpath internal proxy for subdomains, but redirect external clients if they ask for that subpath?

  - by HostileFork

  I have a VirtualHost that I'd like to have several subdomains on. (For the sake of clarity, let's say my domain is example.com and I'm just trying to get started by making foo.example.com work, and build from there.) The simplest way I found for a subdomain to work non-invasively with the framework I have was to proxy to a sub-path via mod_rewrite. Thus paths would appear in the client's URL bar as http://foo.example.com/(whatever) while they'd actually be served http://foo.example.com/foo/(whatever) under the hood. I've managed to do that inside my VirtualHost config file like this: ServerAlias *.example.com RewriteEngine on RewriteCond %{HTTP_HOST} ^foo\.example\.com [NC] # <--- RewriteCond %{REQUEST_URI} !^/foo/.*$ [NC] # AND is implicit with above RewriteRule ^/(.*)$ /foo/$1 [PT] (Note: It was surprisingly hard to find that particular working combination. Specifically, the [PT] seemed to be necessary on the RewriteRule. I could not get it to work with examples I saw elsewhere like [L] or trying just [P]. It would either not show anything or get in loops. Also some browsers seemed to cache the response pages for the bad loops once they got one... a page reload after fixing it wouldn't show it was working! Feedback welcome—in any case—if this part can be done better.) Now I'd like to make what http://foo.example.com/foo/(whatever) provides depend on who asked. If the request came from outside, I'd like the client to be permanently redirected by Apache so they get the URL http://foo.example.com/(whatever) in their browser. If it came internally from the mod_rewrite, I want the request to be handled by the web framework...which is unaware of subdomains. Is something like that possible?

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• Apache2: Limit simultaneous requests & throttle bandwidth per IP/client?

  - by xentek

  I want to limit simultaneous requests & throttle bandwidth per IP/Client on a single apache vhost. In other words, I want to ensure that this site, which hosts large media files, doesn't get hammered by someone trying to download everything all at once (just happened the other night). I'd like to limit the outgoing transfer speed overall for this site, as well as limit the number of connections a single IP can make to the server to a sane default (i.e. within normal browser limits for multiple requests so page loads aren't effected too much). Bonus points if I can actually scope it to file types (i.e. leave web files alone, but apply these rules to just the media files). We're running Ubuntu 9.04 on all the servers, and have two apache/php servers being load balanced via Round Robin by a squid proxy server. MySQL is running on its own box as well. We've got plenty of bandwidth to give them, so I don't really want overall caps, but just want to throttle the amount of memory/CPU it takes to serve this site. There other sites on these servers that we don't want to apply these rules too, just want to keep this one from hogging all the resources. Let me know if you need more info! Thanks in advance for your suggestions!

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• Squid reverse proxy array - siblings not communicating with each other

  - by V. Romanov

  I want to set up 2 squid servers to act as reverse proxy and cache for a webserver on our intranet. The load balancing will be done with DNS round robin or just different mappings for different clients. The thing is, I want both servers to try and contact each other to see if they have the object required in cache before contacting the webserver for it (the network that servers the webserver is the bottleneck and I'm trying to eliminate it) Both squids are configured the same, here are the relevant config lines : acl dvr1_cache_it_best_tv_com dstdomain dvr1.cache.it.best-tv.com acl squid1_it_best_tv_com dstdomain squid1.it.best-tv.com acl squid2_it_best_tv_com dstdomain squid2.it.best-tv.com http_access allow dvr1_cache_it_best_tv_com http_access allow squid1_it_best_tv_com http_access allow squid2_it_best_tv_com http_access allow all http_port 8081 accel defaultsite=dvr1.cache.it.best-tv.com cache_peer dvr1.origin.it.best-tv.com parent 80 0 no-query originserver name=Proxy_dvr1_origin_it_best_tv_com cache_peer squid1.it.best-tv.com sibling 8081 3130 weight=10 name=Proxy_Squid1_it_best_tv_com cache_peer squid2.it.best-tv.com sibling 8081 3130 weight=10 name=Proxy_Squid2_it_best_tv_com cache_peer_access Proxy_dvr1_origin_it_best_tv_com allow dvr1_cache_it_best_tv_com cache_peer_access Proxy_squid1_it_best_tv_com allow squid1_it_best_tv_com cache_peer_access Proxy_squid1_it_best_tv_com allow squid2_it_best_tv_com cache_peer_access Proxy_squid1_it_best_tv_com allow dvr1_cache_it_best_tv_com cache_peer_access Proxy_squid2_it_best_tv_com allow squid1_it_best_tv_com cache_peer_access Proxy_squid2_it_best_tv_com allow squid2_it_best_tv_com cache_peer_access Proxy_squid2_it_best_tv_com allow dvr1_cache_it_best_tv_com just to make it clear - dvr1.cache is the alias for the proxy servers. dvr1.origin is the web server. Both servers work, both serve content and cache it and work fine. However, when I clear the cache on one server and then access it, it gets the content from the parent (DVR1_ORIGIN) instead of going to the sibling squid. What did I configure wrong? Or perhaps I don't understand the architecture correctly? I read the squid manuals but as far as I see i did it all by the book and yet it doesn't work right. Any help will be appreciated!

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• How browsers handle multiple IPs

  - by Sandman4

  Can someone direct me to information on exact browsers behavior when browser gets multiple A records for a given hostname (say ip1 and ip2), and one of them is not accessible. I interested in EXACT details, like (but not limited to): Will browser get 2 IPs from OS, or it will get only one ? Which ip will browser try first (random or always the first one) ? Now, let's say browser started with the failed ip1 For how long will browser try ip1 ? If user hits "stop" while it waits for ip1, and then clicks refresh which IP will browser try ? What will happen when it times-out - will it start trying ip2 or give error ? (And if error, which ip will browser try when user clicks refresh). When user clicks refresh, will any browser attempt new DNS lookup ? Now let's assume browser tried working ip2 first. For the next page request, will browser still use ip2, or it may randomly switch ips ? For how long browsers keep IPs in their cache ? When browsers sends a new DNS request, and get SAME ips, will it CONTINUE to use the same known-to-be-working IP, or the process starts from scratch and it may try any of the two ? Of course it all may be browser dependent, and may also vary between versions and platforms, I'd be happy to have maximum of details. The purpose of this - I'm trying to understand what exactly users will experience when round-robin DNS based used and one of the hosts fails. Please, I'm NOT asking about how bad DNS load balancing is, and please refrain from answering "don't do it", "it's a bad idea", "you need heartbeat/proxy/BGP/whatever" and so on.

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• Good Enough Failover Strategy for DNS / MySQL / Email

  - by IMB

  I've asked and read a lot questions regarding DNS failover but the more I read the more complicated it becomes, some people say it's good enough some say it isn't. No clear answers from what I read. I was wondering if we can set it straight once and for all, at least for the requirements of most websites out there. Right now let's assume the following: We don't need really need load-balancing, what we need is a failover solution. We are running a website based on LAMP on a VPS. We need to make sure that the Web Server, MySQL, Email are always accessible if not 99%. Basically here's my idea and questions about it: Web Server: We need at least one failover server (another VPS on a separate data center). Is DNS Failover via Round Robin good, if not, what's the best? And how do you exactly implement it? How do you make the files you upload/delete on Server A is also on Server B? MySQL: I've only read a brief intro to MySQL replication and I assume that I can replicate Server A to Server B and vice versa on the fly right? So just it case Server A fails and Server B is now running, it will continue to work and replicate to Server A when it becomes available. So in essence Server B is now the primary server, and will later on failover to Server A, should a failure happen again. Email: If we are gonna use DNS Failover, using webmail or relying on emails stored on the server is probably not a good idea right? Since some emails might be on Server A while some might be on Server B? I assume a basic email forwarder to a 3rdparty is good enough (like Gmail for example) to ensure all emails are kept in one place. Here's a basic diagram for a better picture: http://i.stack.imgur.com/KWSIi.png

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• Webcam security camera software that runs as a service

  - by hurfdurf

  I've been looking for Windows webcam software that will run as a Windows service without any user login. The goal is to use the webcam as a cheap security camera and log the results to secure networked storage (windows share, not FTP). The requirements are: Motion detection Video capture Runs as a service (should start recording immediately after reboot) Nice to have: Round-robin storage, e.g. 10Gb limit, oldest files overwritten/deleted when space gets low I've read the other webcam questions but still haven't stumbled across anything suitable. Evaluations thus far: Title MotionDetect Service Snapshots Video SpaceLimit License Yawcam Yes Yes Yes No No GPL WebCam ZoneTrigger Yes No Yes Yes No Commercial Dorgem Yes No Yes Yes No GPL AbelCam Yes No Yes Yes No Commercial Logitech Yes No Yes Yes No Paired with camera IspyConnect Yes No Yes Yes Yes Free SecureCam (SourcefoYes No Yes Yes No GPL AbelCam Yes No Yes Yes No Commercial Active WebCam Yes Yes(?) Yes Yes Volume Free Commercial WebCam Surveyor Yes No Yes Yes No Commercial WebCamsPy NA NA NA NA NA GPL Camera: Logitech Webcam Pro 9000 Windows 7 32-bit WebCamsPy failed to initialize so couldn't be tested So far, the contenders: Active Webcam comes the closest, and claims to run as a service, but i haven't been able to get it to record after a cold boot even though a service is running. Yawcam can be set up as a service but doesn't record video. IspyConnect has exactly the type of space limit I want and looks great, but doesn't run as a service (seems also to be a bit of a cpu hog) Any other suggestions? I'm locked into Windows so can't use linux Motion, which looks almost perfect. Any pointers to rich Windows webcam/motion detection libraries out there that could easily be turned into a command line program would also be appreciated.

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• Nginx proxy upstream cached?

  - by Julian H. Lam

  Attempting to resolve an issue that's been annoying me for a bit. I've distilled the symptoms into a set of reproducible steps: I have two sites, siteA, and siteB. They are both Node.js applications running on different ports (for the sake of example, 4567 and 4568) Both applications have their own file in sites_available (plus a symlink from sites_enabled), which contain the directives proxy_pass http://node_siteA/ and proxy_pass http://node_siteB/ respectively, inside of a location block. They also each have an upstream block (defined globally?): upstream node_siteA { upstream node_siteB { server 127.0.0.1:4567; server 127.0.0.1:4568; } } Site A and Site B have nothing to do with each other. Yes, I am restarting (reloading, actually) nginx every time I make a change. If I take down site B and attempt to access it via the web, I am served site A. Why is this? Thoughts Other times, when I create a new Site C, for example, nginx refuses to show me anything except "Welcome to nginx!" for ~5 minutes. This suggests a resolver timeout, perhaps? When I access Site B after its config has been deleted, and it sends me to Site A, this sounds like nginx sending me to servers in a round-robin fashion...

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• How is network mounted software executed?

  - by CptSupermrkt

  I would like to understand how network mounted software works. For example, at my place of work, we have a software server. Each client machine (hundreds of them) automatically mounts directories from the software server on boot. For example, a program like Matlab is installed just once on the software server, but each client machine can start up an instance of Matlab. What is going on under the hood? Let's say I run /opt/bin/matlab and /opt/ is mounted from the software server, what happens when I press Enter to execute matlab on a client machine? The process is on the client machine, and I've already narrowed down that there isn't any implicit or hidden file transfer (i.e. copying matlab to my machine temporarily for that session) by running matlab on a computer with nearly zero disk space (i.e. not enough room to transfer). Since Matlab was installed on the server, how is my client computer executing it? What mechanism is controlling this? What is happening behind the scenes?

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• Encrypted Windows 7 & Linux Advice Wanted

  - by Miles

  I would like to set up my laptop to dual boot Arch Linux and Windows 7 with file sharing and encryption. Just wanted some advice on going about this because I have not dealt with encryption nor file sharing. I have two 500GB hard drives, and this is my plan: Install Windows 7 across both hard drives Use a live CD to wipe out Windows boot loader and replace with Grub Legacy Use live CD to wipe out second hard drive and re-size the Windows partition located on first hard drive Install Arch Linux along side with Windows 7 on first hard drive, all remaining space goes to home folder as ext2 Install truecrypt and ext2fsd Concerns: Is this the most efficient way to share files between both OSes? Or should I just be using NTFS to store all my data? How would the file permissions work when sharing files between Windows and Linux? Is there a high likley hood of corruption, and what is the ease of backing up files from an encrypted disk? Anything I should look out for, conflict between Grub and Truecrypt? Thank you for any advice, and feel free to post any links you might find useful to me. I am trying to plan this out so I can minimize downtime as I do not want to spend more than a night on this, nor do I want to run into a major problem some time in the future.

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• Apache Server with memcache, varnish and php slow request times

  - by coolestdude1

  My issue is that these servers are taking rather long for request about 2 seconds on average just to serve files. When we had just one server doing everything it was noticeably faster even with the same web app (Drupal 6 and Drupal 7). I want to get this number down to a reasonable level and so I need some help getting to the bottom of why the request times are so slow. This can cause the webapp to hang on post or put and generally leads to a bad user experience on my sites. PS: I am more of a server newbie so this has confounded me for quite some time. The domains: collabornation.net nptrainingworks.com (they run off the same two webservers using vhost configs) The Gear: Two Rackspace 4 Gig servers running CentOS 6.2 Final They have a mounted file system (gluster) that is used to keep files the same on both machines. They are behind a rackspace load balancer running round robin. Mysql is run using php-pdo and php-mysql as such mysql is run on another instance running memcache on that machine with phpMyAdmin located there as well. Apache version number 2.2.15-15.el6.centos.1 (httpd.x86_64) Varnish version number 3.0.2-1.el5 (varnish.x86_64) PHP version number 5.3.14-1.el6.remi (php.x86_64) Configs Linked Below Apache Conf Vhost Conf Varnish Backends Varnish Defaults Varnish Acl PHP INI Again need some help, much appreciated!

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• Apache load balancer with https real servers and client certificates

  - by Jack Scheible

  Our network requirements state that ALL network traffic must be encrypted. The network configuration looks like this: ------------ /-- https --> | server 1 | / ------------ |------------| |---------------|/ ------------ | Client | --- https --> | Load Balancer | ---- https --> | server 2 | |------------| |---------------|\ ------------ \ ------------ \-- https --> | server 3 | ------------ And it has to pass client certificates. I've got a config that can do load balancing with in-the-clear real servers: <VirtualHost *:8666> DocumentRoot "/usr/local/apache/ssl_html" ServerName vmbigip1 ServerAdmin [email protected] DirectoryIndex index.html <Proxy *> Order deny,allow Allow from all </Proxy> SSLEngine on SSLProxyEngine On SSLCertificateFile /usr/local/apache/conf/server.crt SSLCertificateKeyFile /usr/local/apache/conf/server.key <Proxy balancer://mycluster> BalancerMember http://1.2.3.1:80 BalancerMember http://1.2.3.2:80 # technically we aren't blocking anyone, but could here Order Deny,Allow Deny from none Allow from all # Load Balancer Settings # A simple Round Robin load balancer. ProxySet lbmethod=byrequests </Proxy> # balancer-manager # This tool is built into the mod_proxy_balancer module allows you # to do simple mods to the balanced group via a gui web interface. <Location /balancer-manager> SetHandler balancer-manager Order deny,allow Allow from all </Location> ProxyRequests Off ProxyPreserveHost On # Point of Balance # Allows you to explicitly name the location in the site to be # balanced, here we will balance "/" or everything in the site. ProxyPass /balancer-manager ! ProxyPass / balancer://mycluster/ stickysession=JSESSIONID </VirtualHost> What I need is for the servers in my load balancer to be BalancerMember https://1.2.3.1:443 BalancerMember https://1.2.3.2:443 But that does not work. I get SSL negotiation errors. Even when I do get that to work, I will need to pass client certificates. Any help would be appreciated.

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• What are the typical methods used to scale up/out email storage servers?

  - by nareshov

  Hi, What I've tried: I have two email storage architectures. Old and new. Old: courier-imapds on several (18+) 1TB-storage servers. If one of them show signs of running out of disk space, we migrate a few email accounts to another server. the servers don't have replicas. no backups either. New: dovecot2 on a single huge server with 16TB (SATA) storage and a few SSDs we store fresh mails on the SSDs and run a doveadm purge to move mails older than a day to the SATA disks there is an identical server which has a max-15min-old rsync backup from the primary server higher-ups/management wanted to pack in as much storage as possible per server in order to minimise the cost of SSDs per server the rsync'ing is done because GlusterFS wasn't replicating well under that high small/random-IO. scaling out was expected to be done with provisioning another pair of such huge servers on facing disk-crunch issues like in the old architecture, manual moving of email accounts would be done. Concerns/doubts: I'm not convinced with the synchronously-replicated filesystem idea works well for heavy random/small-IO. GlusterFS isn't working for us yet, I'm not sure if there's another filesystem out there for this use case. The idea was to keep identical pairs and use DNS round-robin for email delivery and IMAP/POP3 access. And if one the servers went down for whatever reasons (planned/unplanned), we'd move the IP to the other server in the pair. In filesystems like Lustre, I get the advantage of a single namespace whereby I do not have to worry about manually migrating accounts around and updating MAILHOME paths and other metadata/data. Questions: What are the typical methods used to scale up/out with the traditional software (courier-imapd / dovecot)? Do traditional software that store on a locally mounted filesystem pose a roadblock to scale out with minimal "problems"? Does one have to re-write (parts of) these to work with an object-storage of some sort - such as OpenStack object storage?

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• apache/httpd responds slower under EL6.1 than EL5.6 (centos)

  - by daniel

  I've read through other threads on performance differences between RHEL6 and RHEL5, but none seem a tight match to mine. My issue manifests itself in slightly slower average response time (20ms) per request. I have about 10/10 servers of the same hardware spec with Cent6.1 and Cent5.6. The issue is consistent across the group. I am running Ruby on Rails with Passenger. Apache config is identical (checked out from the same SVN repo) Ruby and Passenger are identical builds. Application is identical and being served traffic round robin. mod_worker An interesting clue from server-status: The Cent6.1 servers have a steady 20-40 threads in the "Reading Request" state while the Cent5.6 servers have around 1. I'm graphing this so I can see it trend over time. I also have a bunch of much newer machines that are significantly faster and are running Cent6.1. They dust all the older machines in response time, but I can see they also have a steady 20-40 threads in the "Reading Request" state. This makes me believe I can get their response time down, if I can figure out what is holding up these requests. My gut is telling me that I need to tune some network setting in sysctl, but I haven't figured it out yet. Help is appreciated.

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• Where can someone store >100GB of pictures online? [closed]

  - by sbi

  A person who is not very computer-savvy needs to store 130GB of photos. The key parameters are: an non-negligible probability that the company selling the storage will be existing, and the data accessible, for at least five years data should be considered safe once uploaded reasonable terms of service: google drive reserving the right to literally do anything they want with their user's data is not acceptable; the possibility that the CIA might look at those pictures is not considered a threat easy to use from Windows, preferably as a drive no nerve-wracking limitations ("cannot upload 10GB/day" or "files 500MB" etc.) that serve no purpose other than pushing the user to the next-higher price plan some upgrade plan: there's currently 10-30GB of new photos per year, with a tendency to increase, which might bust a 150GB limit next January ability to somehow sort the pictures: currently they are sorted into folders, but something alike (tags) would be just as good, if easy enough to apply of course, the pricing is important (although there's a reason this is the last bullet; reasonable data safety is considered more important) Nice to have, but not necessary features would be: additional features related to photos (thumbnail generation, album sharing etc.) access from web and other platforms than Windows (smart phones) Let me stress this again: The person in need of that is able to copy pictures from the camera to the computer, can copy files in the explorer, and uses a web email service. That's about it, there's almost no understanding of what happens under the hood.

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• Multi-petabyte scale out storage solution [closed]

  - by Alex Yuriev

  Let's say that I have a need to have a single-name space scale to multi-petabyte object store with a file system-like wrapper. What is currently out there that supports the following: Single name space that can take 1B files. Support for multiple entry points using NFS At least node level replication ( preferably node and file level replication ) Online software upgrades No "magic sauce" on the storage layer The following has been evaluated: Gluster & Lustre - just ick - fundamental lack of understanding of why online upgrades are mandatory. OneFS - we have it. It is smelling more and more like it hides a dead body under the hood. Other than MapR and zfs am I missing anything? P.S. Oh yes, I keep forgetting that the forums are for people to discuss if 2TB drive actually stores 2TB info. May bad. Seriously though - how the heck can "meets the following requirements" can be considered a "debate"? P.P.S. I did not throw an idiotic insult - i pointed out that this is actually an interesting question compared to a conversation about storage capacity of a 2TB hard drive. It is not a question of what works better - it is a question that asks did I miss any of the products that currently exist which fit the criteria where criteria is clearly outline. I got one answer below which included something that I have not looked at in a long time which looks quite a bit grown up compared to the time I briefly look at it before.

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