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• IP queue buffer

  - by summerbulb

  I seem to have an issue with IP queue. I have a linux machine that I am using to run some experiments. The linux machine is configured to be a router, having two NICs, connecting two other computers, and managing their network traffic. All incoming packages are captured, using iptables, and analyzed by a C application. The application analyzing the packets has a built-in delay, as part of the experiment. So I have one very fast computer sending packets through my linux-router and a (relatively) slow linux-router that analyses and deals with the packets, one by one. This situation leads to the fact that when I fire up a sender application on one of the computers connected to the linux-router, my IP queue on the linux-router gets filled up (almost) instantaneously. The IP queue's max length is currently set to 1024, and if it overflows, the packets are dropped. This is expected and i'm OK with it. But, (and this is where it gets interesting), every now and then I get the following error: "Failed to receive netlink message: No buffer space available" At start, I thought this was due to the IP queue overflow, but after some analysis i found that sometimes I get the error even if the IP queue buffer did not overflow, and sometime I DON'T get the message even though the buffer DID overflow. When I run > cat /proc/net/ip_queue, I get the following table (also used to monitor the IP queue overflow): Peer PID : 27389 Copy mode : 2 Copy range : 65535 Queue length : 0 Queue max. length : 1024 Queue dropped : 1166875 Netlink dropped : 2916 Looking at the last two values, Queue dropped seems to refer to packets that did not manage to get into the IP queue because the buffer was full. I can see this value rise as I bombard the linux-router. Netlink dropped ( as it's name implies :) ) seems to have to do with the error i'm getting. I did my best to search for material on this error, but wasn't able to find anything that seemed to point me in the required direction. Bottom line: Why am I getting this error and what can I do to avoid it?

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• When should NTPd broadcast/broadcastclient be used instead of client/server or peer modes?

  - by Luke404

  The NTP deamon if often used in its simplest mode, which is client/server: you specify one or more server directives in your ntp.conf and your clients will use those servers. In addition to that, when you run your own NTP servers, it is good practice to peer them together, so if one of them looses connectivity to its upstream servers, it will get time from its peers. But NTPd can also work with broadcast and/or multicast distribution of time data, with the documentation stating: broadcast and multicast modes are intended for configurations involving one or a few servers and a possibly very large client population The documentation also says elsewhere: It is possible and frequently useful to configure a host as both broadcast client and broadcast server. A number of hosts configured this way and sharing a common broadcast address will automatically organize themselves in an optimum configuration based on stratum and synchronization distance. I can see one obvious administrative benefit: you don't have to manually specify and update your list of NTP servers in the clients ntp.conf, so to me it looks tempting to use broadcast mode even for a small client population (say 5+ clients with 3~4 servers). I expect network traffic to be a little higher with broadcasts instead of client/server associations, but given the usual gigabit ethernet LAN the impact should be negligible unless you have a very very large number of hosts in the same broadcast domain. At the end of the day, when should broadcast mode be used or avoided? Are there pros and cons I haven't seen?

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• Requests per second slower when using nginx for load balancing

  - by Ed Eliot

  I've set up nginx as a load balancer that reverse proxies requests to 2 Apache servers. I've benchmarked the setup with ab and am getting approx 35 requests per second with requests distributed between the 2 backend servers (not using ip_hash). What is confusing me is that if I query either of the backend servers directly via ab I get around 50 requests per second. I've experimented with a number of different values in ab the most common being 1000 requests with 100 concurrent connections. Any idea why traffic distributed across 2 servers would result in fewer requests per second than hitting either directly? Additional info: I've experimented with worker_processes values of between 1 and 8, worker_connections between 1024 and 8092 and have also tried keepalive 0 and 65. My main conf currently looks like this: user www-data; worker_processes 1; error_log /var/log/nginx/error.log; pid /var/run/nginx.pid; worker_rlimit_nofile 8192; events { worker_connections 2048; use epoll; } http { include /etc/nginx/mime.types; sendfile on; keepalive_timeout 0; tcp_nodelay on; gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } I've got one virtual host (in sites available) that redirects everything under / to 2 backends across a local network.

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• EMC VNX iSCSI setup - unsure about SP/port assignment

  - by pauska

  We have a new VNX5300 waiting to get configured, and I need to plan out the network infrastructure before the EMC tech arrives. It has 4x1gbit iSCSI per SP (8 ports in total), and I'd like to get the most out of the performance until we jump over to 10gig iSCSI. From what I can read from the docs - the recommendation is to use only two ports per SP, with 1 active and 1 passive. Why is this? It seems kind of pointless to have quad-port i/o-modules and then recommend to not use more than two of them? Also - I'm a bit unsure about the zoning. The best practices guide state that you should separate each port on each SP from each other on different logical networks. Does this mean that I have to create 4 logical networks to be able to use all 8 ports? It also gives the following example: Does this mean that A0 and B0 should sit on the same physical switch aswell? Won't this make all traffic go on one switch (if both A1 and B1 are passive)? Edit: Another brainpuzzle I don't get it - each host (as in server) should not have more iSCSI bandwidth available than the storage processor. What on earth does this matter? If serverA have 1gbit and serverB have 100mbit, then the resulting bandwith between them is 100mbit. How can this result in some kind of oversubscription? Edit4: Wait, what. Active and passive ports? The VNX runs in a ALUA configuration with asymmetrical active/active.. there shouldn't be any passive ports, only preferred ones..

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• Can't display RSSI values in Wireshark

  - by Giovanni Soldi

  I am trying to analyze the up-link Wireless traffic generated by my Sony Ericsson phone and captured by my D-Link router, on which I installed the DD-WRT firmware. To do this, first I log in the router and enable the prism0 interface by typing the command: wl -i eth1 monitor 1 and then I start to capture the packets by typing: tcpdump -i prism0 ether src xx:xx:xx:xx:xx:xx -s0 -w /tmp/smbshare/sony_ericsson_test.pcap where xx:xx:xx:xx:xx:xx is the MAC address of my Sony Ericsson phone. After a while I transfer the sony_ericsson_test.pcap file to my computer and open it with Wireshark program. In order to display the RSSI values I follow this procedure: Edit - Preferences... - Columns - Press "Add" button - As "Field type" I choose "IEEE 802.11 RSSI" and finally I choose name "Power" and click on "Apply" button. The problem is that the column "Power" is empty with no RSSI values. Does Anyone has a clue on why are RSSI values not displayed? Maybe I am missing a passage. Looking forward to hearing from anyone of you! Thanks in advance for your help!

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• Why does my Intel Tolapai network chip not transmit packets?

  - by Hanno Fietz

  I'm trying to deploy an embedded system (NISE 110 by Nexcom) based on the Intel EP80579 (Tolapai) chip. Tolapai apparently integrates controllers for Ethernet etc. on a single chip (Intel homepage). The machine can't get a network connection. Diagnosis as far as I could manage: Drivers drivers from Intel compiled and installed without problems (version 1.0.3-144). Kernel version and Linux distribution (CentOS 5.2, 2.6.18) match the driver's installation instructions. drivers are loaded and show up in lsmod (module names are gcu and iegbe) interfaces eth0 and eth1 show up in ifconfig ifconfig I can bring up the interfaces with fixed IP pinging the interface locally works ifconfig shows flag UP but not RUNNING Link ethtool shows "Link detected: no", "Speed: unknown (65536)" and "Duplex: unknown (255)" Link LED is on on the other side of the cable, ethtool shows "Link detected: yes" and reports a speed of 1000 Mbps, which has allegedly been auto-neogotiated with the problematic device. Network traffic analysis the device does not reply on ARP, ICMP echo or anything else (iptables is down) when trying to send ICMP or DHCP requests, they never reach the other end activity LED is off on the device, on at the other end. I tried the following without any effect: Different cables (2 straight, one crossed), I get the link LED lit up on each. Three different devices on the other end (one PC, one netbook, one router) Fixed ARP table entries on both sides Connecting both network ports of the machine with each other, won't ping through the cable, but will ping locally. Tried straight and crossed cables for that.

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• What can cause kernel out_of_memory error?

  - by nbolton

  I'm running Debian GNU/Linux 5.0 and I'm experiencing intermittent out_of_memory errors coming from the kernel. The server stops responding to all but pings, and I have to reboot the server. # uname -a Linux xxx 2.6.18-164.9.1.el5xen #1 SMP Tue Dec 15 21:31:37 EST 2009 x86_64 GNU/Linux This seems to be the important bit from /var/log/messages Dec 28 20:16:25 slarti kernel: Call Trace: Dec 28 20:16:25 slarti kernel: [<ffffffff802bedff>] out_of_memory+0x8b/0x203 Dec 28 20:16:25 slarti kernel: [<ffffffff8020f825>] __alloc_pages+0x245/0x2ce Dec 28 20:16:25 slarti kernel: [<ffffffff8021377f>] __do_page_cache_readahead+0xc6/0x1ab Dec 28 20:16:25 slarti kernel: [<ffffffff80214015>] filemap_nopage+0x14c/0x360 Dec 28 20:16:25 slarti kernel: [<ffffffff80208ebc>] __handle_mm_fault+0x443/0x1337 Dec 28 20:16:25 slarti kernel: [<ffffffff8026766a>] do_page_fault+0xf7b/0x12e0 Dec 28 20:16:25 slarti kernel: [<ffffffff8026ef17>] monotonic_clock+0x35/0x7b Dec 28 20:16:25 slarti kernel: [<ffffffff80262da3>] thread_return+0x6c/0x113 Dec 28 20:16:25 slarti kernel: [<ffffffff8021afef>] remove_vma+0x4c/0x53 Dec 28 20:16:25 slarti kernel: [<ffffffff80264901>] _spin_lock_irqsave+0x9/0x14 Dec 28 20:16:25 slarti kernel: [<ffffffff8026082b>] error_exit+0x0/0x6e Full snippet here: http://pastebin.com/a7eWf7VZ I thought that perhaps the server was actually running out of memory (it has 1GB physical memory), but my Cacti memory graph looks OK to me... But strangely the load graph goes through the roof shortly before the kernel crashes: What logs can I look at for more info? Update: Maybe noteworthy - the CPU percentage and network traffic graphs were both normal at the time of the crash. The only abnormality was the average load graph.

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• Best all in one linux based proxy,firewall, dhcp and wins server.

  - by BeStRaFe

  I help to run a lan in Sydney. We have a need for a proxy/gateway solution to allow those pesky games that require internet to work. I have been doing this with an ISA server and it has worked quite well. However now i wish to port this over to run on the same hardware as our cacti / nagios box under a vmware VM. ISA server is horridly nad due to the massive ram and i/o requirement for something is basically port blocking and handing out IP's. The needs are as follows. 1. DHCP 2. WINS (otherwise network devices fight over who is the WINS master) 3. Filtering based in PORT for outbound traffic. 4. Ability to whitelist IP/MAC's for internet access. 5. Web Interface. I had been thinking to use PFSENSE however there is no option for a WINS server and i cbf working my way around bsd.

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• How should I perform database maintenance on a 24x7 system

  - by solublefish

  I'm a software developer who inherited a part-time DBA role. I'm responsible for an application backed by a small, high-volume 24x7 database on SQL Server 2008. While there's other stuff in the DB, the critical piece is a 50GB, 7.5M row table that serves 100K requests/sec during peak load, and about half that at "night". This is 99%+ read traffic, but the writes are constant, and required. I need to be able to perform periodic maintenance without a maintenance window. Say an index rebuild, a job to purge old data, Windows Update, or hardware upgrade. Most of the advice I've seen is along the lines of "MAKE a maintenance window." While I appreciate the sentiment, I hope there's another way. If it will solve this problem, I do have the ability to purchase new hardware or modify the database, the clients (a set of web services servers), and much of the application code (ADO.NET + ASP.NET). I've been thinking along the lines of using the warm spare (or a 3rd server) to do the maintenance, and then "swap" it into production. 1 Synchronize the spare by restoring backups, including a current transaction log. 2 Perform the maintenance tasks. 3 Reconfigure clients to connect to the spare server. Existing connections are finished within a minute or so. 4 The spare server is now the production server. The problem remaining is that the new production server is now out of date by however long it took to perform maintenance. Is there some way that the original production server can be made to queue up changes and merge them to the spare between steps 2 and 3? Any other ideas?

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• MSSQL Timing out, a couple of questions...

  - by user29000

  Hi, About once a week, my MSSQL server is timing out, or rather the machine runs out of RAM. This morning it reached 3.9GB of the available 4, with MSSQL taking up 2.5GB. I'm concerned that i've not configured SQL to release memory as it should, so I ran sp_who2 while the timeouts were occuring to see what process were running. If i could post the CSV datafile i would, however, there were 85 processes in total, mostly related to the Full Text service: FT Gatherer - About 35 of these running under the 'sa' account against the master database with status of either sleeping or background, many were dependant on other processes. Is that normal? MySite database - There were only 5 processes for the one active site/database and all were either sleeping or suspended - but their lastBatch dates were set to 1/12/2020. Is that normal? The datbase is only about 20mb in size the traffic levels are very low, so i'm thinking of maybe limiting the amount of RAM SQL has access to (from unlimted to maybe 2GB). Any thoughts / advise would be appreciated. Mny thanks Ben

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• How to bypass vpn talking to VMWare Guest?

  - by marc esher

  Greetings. Network/VPN n00b question here. I'm running VMWare Workstation with a Guest Windows 2003 Server. It has SQL Server 2000 installed. The sole purpose for this Guest is to house SQL Server... it needn't have internet access or access to any other resources on the network other than the host. When launch Check Point VPN software, the host routes through the company network before it connects to the guest ... i.e. it's no longer a direct connection. I assume this is just how things are supposed to work. However, what's happening is that the connection between my host and the SQL Server instance on the guest intermittently drops. It's not consistent, and some databases on the server will be responsive while others aren't. It appears that the databases with the most traffic on the guest (the ones I'm hitting with load tests) are the ones that become intermittently unresponsive. This problem only manifests when VPN is on; when it's off, I can pound away on this database with no troubles. Thanks for any advice!

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• How to access a port via OpenVpn only

  - by Andy M

  I've set up an openvpn server alongside an apache website that can only be accessed on port 8100 on the same machine. My /etc/openvpn/server.conf file looks like this: port 1194 proto tcp dev tun ca ./easy-rsa2/keys/ca.crt cert ./easy-rsa2/keys/server.crt key ./easy-rsa2/keys/server.key # This file should be kept secret dh ./easy-rsa2/keys/dh1024.pem # Diffie-Hellman parameter server 10.8.0.0 255.255.255.0 ifconfig-pool-persist ipp.txt # make sure clients can still connect to the internet push "redirect-gateway def1 bypass-dhcp" keepalive 10 120 comp-lzo persist-key persist-tun status openvpn-status.log verb 3 Now I tried to let only clients connected to the vpn network access the website on apache via port 8100. So I defined a few iptables rules: #!/bin/sh # My system IP/set ip address of server SERVER_IP="192.168.0.2" # Flushing all rules iptables -F iptables -X # Setting default filter policy iptables -P INPUT DROP iptables -P OUTPUT DROP iptables -P FORWARD DROP # Allow incoming access to port 8100 from OpenVPN 10.8.0.1 iptables -A INPUT -i tun0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o tun0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT # outgoing http iptables -A OUTPUT -o tun0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -i tun0 -p tcp --sport 80 -m state --state ESTABLISHED -j ACCEPT Now when I connect to the server from my client computer and try to access the website on 192.168.0.2:8100, my browser can't open it. Will I have to forward traffic from tun0 to eth0? Or is there anything else I'm missing?

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• Debian, 2 NICs load-balancing or agregating with one same gateway

  - by pouney

  Hi, I have one server, with double NICs connected to one switch with the same gateway. Behind the switch we have internet. |Debian| - eth0 - switch - internet - eth1 - same I don't understand how to load-balancing between eth0 and eth1. The inbound/outbound traffic always use eth1. This is the config: # The primary network interface allow-hotplug eth0 auto eth0 iface eth0 inet static address 192.168.248.82 netmask 255.255.255.240 network 192.168.248.80 broadcast 192.168.248.95 gateway 192.168.248.81 allow-hotplug eth1 auto eth1 iface eth1 inet static address 192.168.248.83 netmask 255.255.255.240 network 192.168.248.80 broadcast 192.168.248.95 gateway 192.168.248.81 Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.248.80 0.0.0.0 255.255.255.240 U 0 0 0 eth1 192.168.248.80 0.0.0.0 255.255.255.240 U 0 0 0 eth0 0.0.0.0 192.168.248.81 0.0.0.0 UG 0 0 0 eth1 0.0.0.0 192.168.248.81 0.0.0.0 UG 0 0 0 eth0 Ips aren't real, it's just for the example. Anybody have an idea on correct routing to use eth0 on 192.168.248.82 and eth1 on 192.168.248.83 ? I have many example for multiple gateway but here it's the same. Thanks all. Regards

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• OpenVZ with bridged interfaces and VLAN

  - by Deimosfr

  Hi, I've got a problem with OpenVZ with bridged VLAN. Here is my configuration: +------+ +-------+ +-----------+ +---------+ br0 |VE101 | | | | OpenBSD |----->| Debian |------->| | | WAN |--->| Router | | OpenVZ | +------+ | | | Firewall |----->| br0 br1 | br1 +------+ +-------+ +-----------+ +---------+------->|VE102 | |br0 | | |VLAN br0.110 +------+ v +---------+ |VE103.110| +---------+ I can't make VLAN work on br0 (br0.110) and I would like to understand why. I don't have any switch so no problem with unmanageable switch. I've configured a VLAN interface on OpenBSD in /etc/hostname.vlan110: inet 192.168.110.254 255.255.255.0 NONE vlan 110 vlandev sis1 And it seems to be working fine. I've also adapted my PF configuration to work with VLAN but I don't see any incoming traffic. On my Debian Lenny, here is my interfaces configuration : # The loopback network interface auto lo iface lo inet loopback # br0 auto br0 iface br0 inet static address 192.168.100.1 netmask 255.255.255.0 gateway 192.168.100.254 network 192.168.100.0 broadcast 192.168.100.255 bridge_ports eth0 bridge_fd 9 bridge_hello 2 bridge_maxage 12 bridge_stp off # VLAN 110 auto br0.110 iface br0.110 inet static address 192.168.110.1 netmask 255.255.255.0 network 192.168.110.0 gateway 192.168.110.254 broadcast 192.168.110.255 pre-up vconfig add br0 110 post-down vconfig rem br0.110 It looks OK, but when I start my VE, here is the message: ... Configure veth devices: veth103.0 Adding interface veth103.0 to bridge br0.110 on CT0 for VE103 can't add veth103.0 to bridge br0.110: Operation not supported VE start in progress... So I've got one error here. I've followed this documentation http://wiki.openvz.org/VLAN but it doesn't work. I've certainly missed something but I don't know why. Someone could help me please? Thanks

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• Production deployment to EC2 with minimal downtime

  - by jensendarren

  I have a simple web application deployed on a large instance with EC2. I now want to deploy the latest code to this server but I want to do this in a way which minimizes downtime and is a smooth as possible for the end user. Here is my plan: Fire up another large instance Install all the software layers on that instance Restore and attach an EBS drive to the instance Deploy our latest production ready code on the new instance Run all tests (including manual testing of the application) (If tests pass) Put a "Site Under Maintenance" notice on the live site. Backup the EBS instance on the live site Detach the EBS instance from the new server and replace with the latest backup Use ec2-associate-address to move the IP address to the new instance Sit back and wait for traffic to start flowing though the new instance Terminate the old instance Does this seem like a good strategy? Are there any tutorials or books that might cover this topic? I have already read Cloud Application Architectures by George Reese, which is an excellent book, but does not cover deployment. Additionally, I know that there are tools that can help with this like RightScale or enStratus which I will use when I start using more than one instance.

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• configuring lighttpd for large downloads

  - by ahmedre

  i run a web site that hosts pages that are just general scripts (php, etc) and mp3 downloads (some of which are fairly large - up to 200mb). i am running lighttpd on the servers on linux (ubuntu 64). everything is fine, but under high load, the server is not accessible (or very slow - even sshing in takes a while), and i am guessing this is due to a huge number of mp3 downloads at that time. consequently, dns sees the server as down and redirects all the traffic to the other servers, and after a while, it comes back up and things work again. so what's the best way to fix this? ideally, i want the server to continue running (and the web pages - php etc - to always work, but downloads don't always have to work). should i just have 2 web servers running (one for the downloads and one for the php pages), or is it perhaps something i can fix in my lighttpd configuration? here are the snippets from my configuration: server.max-worker = 4 server.max-fds = 2048 server.max-keep-alive-requests = 4 server.max-keep-alive-idle = 4 server.stat-cache-engine = "fam" fastcgi.server = ( ".php" => (( "bin-path" => "/usr/bin/php-cgi", "socket" => "/tmp/php.socket", "max-procs" => 1, "idle-timeout" => 20, "bin-environment" => ( "PHP_FCGI_CHILDREN" => "64", "PHP_FCGI_MAX_REQUESTS" => "1000" ), "bin-copy-environment" => ( "PATH", "SHELL", "USER" ), "broken-scriptfilename" => "enable" )) ) # normal php site $HTTP["host"] =~ "bar.com" { server.document-root = "/usr/local/www/sites/bar.com/" accesslog.filename = "|/usr/sbin/cronolog /var/log/lighttpd/%m/%d/%H/bar.log" } # download site $HTTP["host"] =~ "(download|stream).foo.com" { server.document-root = "/home/audio/" dir-listing.activate = "enable" dir-listing.hide-dotfiles = "enable" evasive.max-conns-per-ip = 1 evasive.silent = "enable" # connection.kbytes-per-second = 256 accesslog.filename = "|/usr/sbin/cronolog /var/log/lighttpd/%m/%d/%H/download.log" }

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• Ubuntu 12.04 open port 80 inside WLAN

  - by Eduard

  I have an nginx server running on ubuntu 12.04 that serves http through port 80 and https through port 443. Everything works fine if I access it from the same computer via localhost, 127.0.0.1 or the local IP 192.168.0.11. If I try to access the server from another computer in the same VLAN it does not work for http; it works for https. I have changed my nginx configuration to also listen to port 8000 for http; I can then access http from the other computer in the same VLAN via "http://192.168.0.11:8000". I also have a web server running on port 80 on a windows machine and can access it from another device in the same VLAN, therefore the router is not blocking incoming http traffic. The nginx process is run by root. I have used tcpdump and I see that packets are arriving to Ubuntu: 192.168.0.16.49735 192.168.0.11.80 and that some response is being given 192.168.0.11.80 192.168.0.16.49735 (I do not know what the response is though). There is no request arriving at the nginx web server (I have checked the access log). I have iptables empty. I have unsuccessfully tried to find a solution for a long time to this, it has now become a matter of happiness or bitterness :).

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• Dynamically blocking excessive HTTP bandwidth use?

  - by Jeff Atwood

  We were a little surprised to see this on our Cacti graphs for June 4 web traffic: We ran Log Parser on our IIS logs and it turns out this was a perfect storm of Yahoo and Google bots indexing us.. in that 3 hour period, we saw 287k hits from 3 different google ips, plus 104k from yahoo. Ouch? While we don't want to block Google or Yahoo, this has come up before. We have access to a Cisco PIX 515E, and we're thinking about putting that in front so we can dynamically deal with bandwidth offenders without touching our web servers directly. But is that the best solution? I'm wondering if there is any software or hardware that can help us identify and block excessive bandwidth use, ideally in real time? Perhaps some bit of hardware or open-source software we can put in front of our web servers? We are mostly a windows shop but we have some linux skills as well; we're also open to buying hardware if the PIX 515E isn't sufficient. What would you recommend?

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• Google bots are severely affecting site performance

  - by Lynn

  I have an aggregate site on a linux server that pulls in feeds from a universe of about 2,000 blogs. It's in Wordpress 3.4.2 and I have a cron job that is staggered to run five times an hour on another server to pull in the stories and then publish them to the front page of this site. This is so I didn't put too much pressure all on one server. However, the Google bots, which visit a few times every hour bring the server to its knees in the morning and evenings when there is an increase in traffic on the site. The bots have something like 30,000 links to follow at this point. How do I throttle the bots to simply grab the new stories off the front page and stop there? EDIT- Details of my server configuration: The way we have this set up is the server that handles all the publishing is an unmanaged instance via AWS. It mounts the NFS server and connects to the RDS to update content, etc. You get to this publishing instance via a plugin that detects the wp-admin link and then redirects you into there. The front end app server also mounts the NFS and requests data from the RDS. It is the only one that has the WP Super Cache on it.... The OS is Ubuntu on the App server and the NFS runs CentOs. The front end is Nginx and the publishing server is Apache.

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• Performance data collection for short-running, ephemeral servers

  - by ErikA

  We're building a medical image processing software stack, currently hosted on various AWS resources. As part of this application, we have a handful of long-running servers (database, load balancers, web application, etc.). Collecting performance data on those servers is quite simple - my go-to- recipe of Nagios (for monitoring/notifications) and Munin (for collection of performance data and displaying trends) will work just fine. However - as part of this application, we are constantly starting up and terminating compute instances on EC2. In typical usage, these compute instances start up, configure themselves, receive a job from a message queue, and then get to work processing that job, which takes anywhere from 15 minutes to over 8 hours. After job completion, these instances get terminated, never to be heard from again. What is a decent strategy for collecting performance data on these short-lived instances? I don't necessarily need monitoring on them - if they fail for whatever reason, our application will detect this and handle re-starting the job on another instance or raising the flag so an administrator can take a look at things. However, it still would be useful to collect information like CPU (user, idle, iowait, etc.), memory usage, network traffic, disk read/write data, etc. In our internal database, we track the instance ID of the machine that runs each job, and it would be quite helpful to be able to look up performance data for a specific instance ID for troubleshooting and profiling. Munin doesn't seem like a great candidate, as it requires maintaining a list of munin nodes in a text file - far from ideal for an environment with a high amount of churn, and for the short amount of time each node will be running, I'd rather keep the full-resolution data indefinitely than have RRD water down the data over time. In the end, my guess is that this will require a monitoring engine that: uses a database (MySQL, SQLite, etc.) for configuration and data storage exposes an API for adding/removing hosts and services Are there other things I should be thinking about when evaluating options? Perhaps I'm over-thinking this, though, and just ought to run sar at 1-minute intervals on these short-lived instances and collect the sar db files prior to termination.

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• Procurve Primary VLAN

  - by fukawi2

  I'm trying to depreciate usage of VLAN 1 on my ProCurve switches; 1 is unused. I understand that VLAN 1 must exist, but I want to remove it from all ports, especially trunks between switches. The problem I have is that stacking does not seem to work without VLAN 1. I have changed the primary VLAN and management VLAN on all the switches: (config)# primary-vlan 42 (config)# management-vlan 42 (config)# no vlan 1 untagged 25 Port 25 is the link between the 2 switches I'm testing with; the stack master and a member switch; I only want tagged traffic between the switches, no untagged frames. show stacking on the master shows all members as "UP" but I can not telnet any of them: Telnet failed: Connection timed out. All switches have manually assigned (static) IP addresses on VLAN 42, and all exist in the same /25 subnet, as does my desktop. I can telnet the switches directly from my desktop to the individual switch IP addresses, just not from the master switch. Do I need to reboot the switches to have the primary-vlan change take effect? Or is there something else I'm missing?

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• Scaling databases with cheap SSD hard drives

  - by Dennis Kashkin

  Hey guys! I hope that many of you are working with high traffic database-driven websites, and chances are that your main scalability issues are in the database. I noticed a couple of things lately: Most large databases require a team of DBAs in order to scale. They constantly struggle with limitations of hard drives and end up with very expensive solutions (SANs or large RAIDs, frequent maintenance windows for defragging and repartitioning, etc.) The actual annual cost of maintaining such databases is in $100K-$1M range which is too steep for me :) Finally, we got several companies like Intel, Samsung, FusionIO, etc. that just started selling extremely fast yet affordable SSD hard drives based on SLC Flash technology. These drives are 100 times faster in random read/writes than the best spinning hard drives on the market (up to 50,000 random writes per second). Their seek time is pretty much zero, so the cost of random I/O is the same as sequential I/O, which is awesome for databases. These SSD drives cost around $10-$20 per gigabyte, and they are relatively small (64GB). So, there seems to be an opportunity to avoid the HUGE costs of scaling databases the traditional way by simply building a big enough RAID 5 array of SSD drives (which would cost only a few thousand dollars). Then we don't care if the database file is fragmented, and we can afford 100 times more disk writes per second without having to spread the database across 100 spindles. . Is anybody else interested in this? I've been testing a few SSD drives and can share my results. If anybody on this site has already solved their I/O bottleneck with SSDs, I would love to hear your war stories! PS. I know that there are plenty of expensive solutions out there that help with scalability, for example the time proven RAM-based SANs. I want to be clear that even $50K is too expensive for my project. I have to find a solution that costs no more than $10K and does not take much time to implement.

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• httpd.config Easy Apache WHM CentOS

  - by jessie

  First let me explain how I got to this situation. I run a Streaming Video Site. Videos are about 100-250MB in size at any given time there are 500 people on the site. So I guess that would make then static. Recently My site started getting really slow and the only way to fix it temporarily was to restart apache. Now there was no change in traffic that could have caused this. My site is not being attacked. My hosting company recomended to implement mpm_mod and suPHP. They did that by using Easy Apache in WHMS. Then everything was working fine but a little slow. I researched around and to my understanding that mpm will do that but be more table. I was told that installing FastCGI would speed things up just enough. Well that made everything worse. The site is slow and time's out. I used WHM and took off fastCGI but its still the same, it seems like everything i do as of now nothing changes. I even did a roll back on the htconfig file but that didn't work. I'm not sure how to fix this. and my hosting network guy wont be able to touch the problem until Tuesday. I have root access.

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• How to manage multiple email addresses on multiple domains in Exchange

  - by CAD bloke

  Using Hosted Exchange Server, mostly because I use an iPhone, webmail & Outlook on 2 laptops. I want to keep everything consistent and unfragmented. Also, I want push notifications. I have 2 domains, a professional one & a personal one. Each domain has about 5 (give or take) email addresses I use for various purposes. Each domain also has a few parked domains (.net, .org, .info) aliased to the .com domain. I would like to keep emails from the 2 domains separated. Do I need an extra mail box, meaning extra expense or can I create another Exchange user on the same mailbox and create an extra account in Outlook? In either case I will have to wait for iOS4 on the iPhone to manage 2 Exchange accounts. Or am I better off just using a set of rules and folders? The aliased domains are another joy to behold entirely. It looks like I will have to add each email address variant individually. Alternatively, I reckon I may just leave the aliased domains at the pop3 host and let Outlook gather those as edge-cases. Surely I can't be the only one making my life this difficult. Anyone out there done this? From the left field - is this (much) easier in gMail? I'm not committed to Exchange (yet). Previously I used Outlook as a pop3 client with a set of filters to direct incoming traffic to folders. This worked with the aliased domains because my host directed all the aliased TLDs to the same mailbox.

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• FTP Server with advanced features

  - by Nikolas Sakic

  Hi, We supply zone-files to our customers. Some zone files are big about 300MB and some are quite small, maybe like 1MB. We had this issue that someone setup a script to continually download the file. Imagine downloading 300MB file a few hundred times a day. Since, we don't have packet-shaper to throttle the traffic, we need to upgrade ftp server and use add-on modules to limit the download somehow. We currently use proftpd server. Also note that there are different users for different domains - say, if you want to download zone file for .INFO domain, then you use a particular user. That user can't download any other zone's file. This is what we are looking for: Have maximum of 400MB download per user per day. Or even have different download limit for different users per day. Have one connection per user at any time. Max # of connection (non-simultaneous) per user per day is 5. Anyone trying to exceed that gets banned for 24 hours. Has anyone used FTP server with similar restrictions above? Does anyone have any ideas where I can start? Any help would be appreciated. Thanks. -N

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