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  • Ram configuration 4x4 or 2x8?

    - by Carl B
    I am looking to upgrade my Ram to 16gigs and I am wondering if there is any distinct advantage of the way I do it. That being a 4x4 or 2x8 set up. In all my searching there have been a number of pros for each profile. I can find no benchmarck results for either setup as a compaison. So, if there are 2 profiles of the same speed, same voltage, same timing and same cas what would perform better or have a better over all benafit? A few examples from my search - a 4x4 set would lend a benafit in that if one stick failed, you only lose 25% of your Ram vs 50% in a 2x8 set up. a 2x8 set up would have less strain on the memory controler and motherboard. a 2x8 would generate less heat. a 2x8 set up is easier to over clock (not part of my need, but alot of the comparisons circled around the overclocability ease of the 2 stick set up). There is one outstanding benafit that I have found in at least the target company I have looked at and that is price. The 2x8 is nearly half the cost. My motherboard supports a max of 16 gigs and I have a 64 bit OS. Has anyone seen any performance comparisons or is 16 gb just 16 gb no matter how you slice it? And is there any merit to the above pros? Edit: as per the mobo specs - Main Memory • Supports four unbuffered DIMM of 1.5 Volt DDR3 800/1066/1333/1600*/1800*/2133* (OC) DRAM, 16GB Max

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  • How do I speed up and cache mmap file access over NFS on Linux?

    - by Zan Lynx
    The server and client are both 64-bit Ubuntu 10.04 LTS. The application in question is a custom app that uses mmap() for fast random file access. Its ideal state is when the entire file is cached in RAM. The network connections are really fast 10Gb Ethernet. It is a virtual server blade setup. It isn't the network connections slowing things down because everything performs superbly when using a virtual disk (iSCSI to the SAN). But when we run the application on a NFS home directory mount, performance goes to the dogs. It appears that the Linux kernel isn't caching anything. So it is reading every single disk block needed by mmap() accesses over and over and over again. The NFS mount is done through autofs, which has only default settings. /proc/mounts shows the NFS mount is done with the following options: rw,relatime,vers=3,rsize=131072,wsize=131072,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.11.52,mountvers=3,mountproto=tcp,addr=192.168.11.52 How can I make Ubuntu 10.04 cache the file instead of reloading it all the time?

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  • Tuning Linux + HAProxy

    - by react
    I'm currently rolling out HAProxy on Centos 6 which will send requests to some Apache HTTPD servers and I'm having issues with performance. I've spent the last couple of days googling and still can't seem to get past 10k/sec connections consistently when benchmarking (sometimes I do get 30k/sec though). I've pinned the IRQ's of the TX/RX queues for both the internal and external NICS to separate CPU cores and made sure HAProxy is pinned to it's own core. I've also made the following adjustments to sysctl.conf: # Max open file descriptors fs.file-max = 331287 # TCP Tuning net.ipv4.tcp_tw_reuse = 1 net.ipv4.ip_local_port_range = 1024 65023 net.ipv4.tcp_max_syn_backlog = 10240 net.ipv4.tcp_max_tw_buckets = 400000 net.ipv4.tcp_max_orphans = 60000 net.ipv4.tcp_synack_retries = 3 net.core.somaxconn = 40000 net.ipv4.tcp_rmem = 4096 8192 16384 net.ipv4.tcp_wmem = 4096 8192 16384 net.ipv4.tcp_mem = 65536 98304 131072 net.core.netdev_max_backlog = 40000 net.ipv4.tcp_tw_reuse = 1 If I use AB to hit the a webserver directly I easily get 30k/s connections. If I stop the webservers and use AB to hit HAProxy then I get 30k/s connections but obviously it's useless. I've also disabled iptables for now since I read that nf_conntrack can slow everything down, no change. I've also disabled the irqbalance service. The fact that I can hit each individual device with 30k/s makes me believe the tuning of the servers is OK and that it must be some HAProxy config? Here's the config which I've built from reading tuning articles, etc http://pastebin.com/zsCyAtgU The server is a dual Xeon CPU E5-2620 (6 cores) with 32GB of RAM. Running Centos 6.2 x64. The private and public interfaces are on separate NICS. Anyone have any ideas? Thanks.

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  • 3dmark score abnormal

    - by Sean
    I just bought a new laptop. It is core i7 3610QM.(Ivy bridge, 4 core plus hyperthreading), 8G ram, nvidia GT 610M 2GB. The OS is Win7 64bit. I ran 3dmark 11, but the score is frustrating. For 1280*720, the score is P730. It is too low right? I searched online, the score should at least above 1000. Am I right? I never use this software before. I know nvidia has optimus, so I made the laptop in high performance state and white-listed the 3dmark program. But there is no help. I am guessing 3dmark is using i7's graphic module. It cannot transform to nvidia. In the running detail of 3dmark, the graphic card cannot be identified(The row remain blank). Can anybody tell me is this the normal case? If not, can I use some other software to test if my nvidia card is working fine? If this nvidia card cannot work, I will return the new laptop asap. Thanks.

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  • pam_ldap.so before pam_unix.so? Is it ever possible?

    - by user1075993
    we have a couple of servers with PAM+LDAP. The configuration is standard (see http://arthurdejong.org/nss-pam-ldapd/setup or http://wiki.debian.org/LDAP/PAM). For example, /etc/pam.d/common-auth contains: auth sufficient pam_unix.so nullok_secure auth requisite pam_succeed_if.so uid >= 1000 quiet auth sufficient pam_ldap.so use_first_pass auth requiered pam_deny.so And, of course, it works for both ldap and local users. But every login goes first to pam_unix.so, fails, and only then tries pam_ldap.so successfully. As a result, we have a well-known failure message for every single ldap user login: pam_unix(<some_service>:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=<some_host> user=<some_user> I have up to 60000 of such log messages per day and I want to change the configuration so, that PAM will try ldap authentication first, and only if it fails - try pam_unix.so (I think it can improve the i/o performance of the server). But if I change common-auth to the following: auth sufficient pam_ldap.so use_first_pass auth sufficient pam_unix.so nullok_secure auth requiered pam_deny.so Then I simply can't login anymore with local (non-ldap) user (e.g., via ssh). Does somebody knows the right configuration? Why Debian and nss-pam-ldapd have pam_unix.so at first by default? Is there really no way to change it? Thank you in advance. P.S. I don't want to disable logs, but want to set ldap authentication on the first place.

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  • Many clients on a wireless AP for UDP broadcast packets

    - by distorteddisco
    I asked this question on StackOverflow and was directed over here, so I'd appreciate any advice. I'm deploying a smartphone application as part of a live music performance that depends on receiving UDP broadcast packets from a wireless access point. I'm guessing that between 20 and 50 clients will be connected at any one time. I'm aware that a maximum of 20 clients per access point is advised, but as the UDP broadcast packets are ground through the LAN, how would I be able to link multiple APs together? I'm looking for recommendations on a suitable AP for this. The actual data transmission rates are very low - only a few kB/s - as I'm just sending small messages to the smartphone apps, and there will be no WAN internet connection. I tried it with a few connected peers on an adhoc wireless connection without any problems, but ran into dropped packet issues on an old WRT54G running ddwrt, though it's in pretty rough shape. What's the best way to do this? I suppose I could limit concurrent wireless connections to 20 clients... but more would be nice. EDIT: I should also say that it's purely one-way communication; the smartphone application is only receiving broadcast packets, not sending anything.

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  • Xen or KVM? Please help me decide and implement the one which is better

    - by JohnAdams
    I have been doing research for implementing virtualization for a server running 3 guests - two linux based and one windows. After trying my hands on Xenserver, I am impressed with the architecture and wanted to use the opensource XEN, which is when I am hearing a lot more about KVM, about how good it is and it's the future etc. So, could anyone here please help me answer some of my queries, between KVM and XEN. Based on my requirement of three VMs on one server, which is better for performance - KVM or XEN, considering one the linux vm's will works a file-server, one as a mailserver and the third one a Windows server? Is KVM stable? What about upgrades.. What about XEN, I cannot find support for it Ubuntu? Are there any published benchmarks on both Xen and KVM? I cannot seem to find any. If I go with Xen, will it possible to move to KVM later or vice versa? In summary, I am looking for real answers on which one I should use.. Xen or KVM?

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  • what are these weird IP address connections in resource monitor?

    - by bill
    I decided to check out Resource Monitor (on the 'Performance' tab in Task Manager, Windows 7) and I noticed in the "Network" section that the 'System' image name kept making a bunch (~5 at a time) of connections to random IP addresses, it would show anywhere from 1-500 bytes/sec 'sent'. They would stay connected for 1-2 minutes. -All web browsers are closed So, first thing I did was run a trace from network-tools.com on some of these IP addresses. 8/10 were outside of US and did not resolve to any host name. Of the 10 IP addresses I traced, 2 were in US, 4 showed origins in China, and one each to Algeria, Russia, Pakistan, Korea. (!) So, the next thing I did was turn off my wireless card, watch the connections disappear, then turn the card back on, and within 30 seconds more random connections were created by System, with different IP addresses from the first time. The next thing I did was go open Task Manager, Show Processes From All Users, then I killed just about everything that wasn't (what appeared to be) a windows process. Turned on wi-fi, and again within 30 seconds, random IP addresses connect for ~ 1 min at a time, new ones coming and going. I occasionally use bit torrent on this machine, but there was definitely no process that seemed related to bt running after I went through task manager, and bt wasn't open to begin with. So, any ideas on what these connections might be for? I have been using Ad-Aware Free and AVG Free on this computer for a while now, always up to date..

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  • SSH & SFTP: Should I assign one port to each user to facilitate bandwidth monitoring?

    - by BertS
    There is no easy way to track real-time per-user bandwidth usage for SSH and SFTP. I think assigning one port to each user may help. Idea of implementation Use case Bob, with UID 1001, shall connect on port 31001. Alice, with UID 1002, shall connect on port 31002. John, with UID 1003, shall connect on port 31003. (I do not want to lauch several sshd instances as proposed in question 247291.) 1. Setup for SFTP: In /etc/ssh/sshd_config: Port 31001 Port 31002 Port 31003 Subsystem sftp /usr/bin/sftp-wrapper.sh The file sftp-wrapper.sh starts the sftp server only if the port is the correct one: #!/bin/sh mandatory_port=3`id -u` current_port=`echo $SSH_CONNECTION | awk '{print $4}'` if [ $mandatory_port -eq $current_port ] then exec /usr/lib/openssh/sftp-server fi 2. Additional setup for SSH: A few lines in /etc/profile prevents the user from connecting on the wrong port: if [ -n "$SSH_CONNECTION" ] then mandatory_port=3`id -u` current_port=`echo $SSH_CONNECTION | awk '{print $4}'` if [ $mandatory_port -ne $current_port ] then echo "Please connect on port $mandatory_port." exit 1 fi fi Benefits Now it should be easy to monitor per-user bandwidth usage. A Rrdtool-based application could produce charts like this: I know this won't be a perfect calculation of the bandwidth usage: for example, if somebody launches a bruteforce attack on port 31001, there will be a lot of traffic on this port although not from Bob. But this is not a problem to me: I do not need an exact computation of per-user bandwidth usage, but an indicator that is approximately correct in standard situations. Questions Is the idea of assigning one port for each user is a good one? Is the proposed setup an reliable one? If I have to open dozens of ports for many users, should I expect a performance drawback? Do you know a rrdtool-based application which could make the chart above?

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  • How to backup virtual machines on a standalone ESXi host?

    - by Massimo
    Standalone ESXi (4.1) host without any vCenter Server. How to backup virtual machines as quickly and storage-friendly as possible? I know I can access the ESXi console and use the standard Unix cp command, but this has the downfall of copying the whole VMDK files, not only their actually used space; so, for a 30-GB VMDK of which only 1 GB is used, the backup would take 30 full GBs of space, and time accordingly. And yes, I know about thin-provisioned virtual disks, but they tend to behave very badly when physically copied, and/or to blow up to their full provisioned size; also, they are not recommended for actual VM performance. It is ok for me to shut down the VMs before backing them up (i.e. I don't need "live" backups); but I need a way to copy them around efficiently; and yes, a way to automate shutdown/startup when taking a backup would also help. I only have ESXi; no Service Console, no vCenter Server... what's the best way to handle this task? Also, what about restores?

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  • Good Hosting Providers With Zend Framework Support [closed]

    - by manyxcxi
    I currently use ixwebhosting for my hosting services. They're cheap and work (most of the time). The databases are horribly slow, the servers are horribly slow, and their support (though usually prompt) is tough to deal with. That being said, they're cheap, I've got like 20 domains hosted in my account, none of them are high volume, and they work JUST good enough- until today. This isn't meant to be a condemnation of ixwh though. Their prices are very low for what they do offer and most things work just fine, most of the time. I need to be able to host web apps written with Zend Framework in a fairly easy fashion. The server performance can't be worse than what I've already had (a pretty low hurdle to clear), and I don't want to spend $30/mo. These are not money making websites- they're projects. My requirements are PHP 5.3, ZF support, MySQL databases, multiple domains- not much. Who should I look at, and who should I look out for?

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  • extra managed+unmanaged switches @ home/office -- best (mis)usage scenario? what would you do?

    - by locuse
    up front -- definitely NOT a mission-critical kind of question. after a 'spring cleaning' of my local office, i've ended up with two 'spare' GigE switches at my home/office -- one managed, capable of VLANs, QoS, etc, and the other unmanaged. i've got more ports than i need. in fact EACH switch has more total ports than i need. but, since i can't have these just sitting around not doing SOMETHING ... ;-) i'm interested in ideas for best combined use of these switches. my local topology is simple: [ net ] -- [ adsl2 modem ] -- [linux firewall/router/DNS ] _______________| | [ some arrangement of the 2 GigE switches ] | ( ... stuff on the lan ... ) [WAP1] [voip ATA] [printer] [desktop1] [mail server] [Xen server [desktop2] ( mostly dev, [desktop3] + file server [desktop4] + media server)] the MailServer is a production mail server the XenServer serves some low vol to the 'net; the MediaServer guest serves ONLY to the LAN is there, e.g., any performance value in segmenting off any of the LAN using the managed switch (VLAN? QoS tagging? something?), feeding the rest into the connected unmanaged switch? or should i simply use one of the switches & be done with it, and use the other for a coffee-cup stand?

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  • Why am I getting a Sharepoint error on a simple "hello world" web page?

    - by Fetchez la vache
    I've been granted admin access to an internal IIS server on which I need to set up a web site. Before doing anything technical I wanted to ensure that I could access the server, but when attempting to access a simple page (that does not refer to Sharepoint) at http://localhost/index.html when logged onto the server directly, I am getting Parser Error Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. Parser Error Message: Could not load file or assembly 'Microsoft.SharePoint' or one of its dependencies. The system cannot find the file specified. Source Error: Line 1: <%@ Assembly Name="Microsoft.SharePoint"%><%@ Application Language="C#" Inherits="Microsoft.SharePoint.ApplicationRuntime.SPHttpApplication" %> Source File: /global.asax Line: 1 Assembly Load Trace: The following information can be helpful to determine why the assembly 'Microsoft.SharePoint' could not be loaded. WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. -------------------------------------------------------------------------------- Version Information: Microsoft .NET Framework Version:2.0.50727.5456; ASP.NET Version:2.0.50727.5456 To be quite honest I know zip about Sharepoint, so why am I getting a sharepoint error on a basic "hello world" html page? Cheers :) Update: I've since supposedly uninstalled Sharepoint, but am still getting this error. Any ideas welcome!

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  • Determining how all memory is used in Windows Server 2008

    - by Mojah
    Hi, I have a Windows Server 2008 system, which has 12GB of RAM. If I list all processes in the Task Manager, and SUM() the memory of each process (Working Set, Memory (Private Working Set), Commit Size, ...), I never reach more than 4-5GB that should be "in use". However, task manager reports this server has 11GB in use via the "Performance" tab. I'm failing in determining where all that used RAM is going. It doesn't seem to be system cache, but I can not be sure. It might be a memory leak in one of the appliances, but I'm struggling to find out which one. The server's memory keeps filing up, and eventually forces us to reboot the device to clear it. I've been reading up on how RAM assignments work on Windows Server: RAM, Virtual Memory, Pagefile and all that stuff: http://support.microsoft.com/kb/2267427 What's the best way to measure? http://www.zdnet.com/blog/bott/windows-7-memory-usage-whats-the-best-way-to-measure/1786 Configure the file system cache in Windows: http://smallvoid.com/article/winnt-system-cache.html But I fear I'm stuck without ideas at the moment.

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  • pgpool2+streaming replication failover on only 2 servers?

    - by aneez
    I am trying to configure pgpool2 and postgresql 9.1 to handle failover. I currently have streaming replication running, and are using pgpool2 for read-only load balancing. I have 2 servers in my setup, both running postgresql - 1 master and 1 slave. The master is also running pgpool2. My question is how do I configure this setup to handle failover? Specifically in the case that the master crashes, and the slave has to take over and run pgpool2 as well. Most documentation and examples I have been able to find assumes that pgpool2 is running on a separate server and thus "never" crashes. I may or may not be attacking the problem using the wrong tools. In my production setup I have a total of 3 identical servers all in independent locations. The main goal of the setup is to achieve a high uptime. Thus failover should be automatic, and bringing a failed node back up should cause only minimal downtime. I want all 3 nodes to be as close to identical as possible, and be able to run with just 1 or 2 nodes available. And if possible I want to use load balancing to improve performance. If anyone can help me gain some insight into how to do this using my current setup or suggest a different/better setup. Thank you!

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  • Oracle: 1 Large Server vs. 2 Smaller Servers?

    - by nvahalik
    We are in the planning stages of setting up our production Oracle 10gR2 environment. Our budget gives us the ability to buy 2 processor licenses of Oracle DB Standard Edition. We have minimal experience with Oracle so I'll defer to anyone who has used it. We are trying to decide if we should set up a single dual quad-core box or 2 individual quad-core boxes in a RAC configuration. Our DB right now is about 60 GB, and at our peak, we'll have up to 150 concurrent users. Most of the big stuff is done via batch processing at night. My gut tells me that having 2 boxes in a RAC configuration can't be a bad thing because it provides a true hardware failover solution. DB stored in a shared LUN on a SAN via iSCSI. Plus if we ever need to add capacity, we already have boxes in place that can be upgraded with extra procs (I assume with zero downtime, since it's set up in a RAC config) if we add extra licenses, or RAM. Does RAC have any performance penalties? Will it add extra latency? Is there any true advantage for having dual processor boxes running these systems? If we build out the Oracle boxes with special hardware: hardware iSCSI cards, TOE NICs, will these boxes be solid? We are deploying on 64-bit Windows. So what would you do? One box or two?

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  • What should I use to ping multiple IPs and get notified of time outs?

    - by HumanVirus
    I've been using MultiPing to ping hundreds of IPs (from access points and such) and check their performance (packet loss, latency) and uptime. The program is very easy to use, but I was wondering if someone could recommend me something that would work better and that would also work in Linux. The features I'm looking for are: Notification Types: At least desktop notifications and SMS, but it would be great if it also had e-mail, IM, or other types of notifications. (MultiPing has some of these, but they don't work too well.) Being notified about the root problem only: Since some devices are dependent on others, I'd like to be notified only about the root problem. E.g. Let's say I have A[x.x.x.222]B[x.x.x.33C[x.x.x.44]D[x.x.x.55], and B goes down, therefore C and D will also be down. Is it possible to get a notification only about B being down? Light on resources. Ideally multiplatform or at least available for both Linux and Windows. I've heard about Nagios and Shinken being used for monitoring. Would you recommend that I use something of the sort or would that be too much for my needs? If using Nagios, Shinken, or similar software is recommended, can anyone tell me what sites I should go to or what books I should get that would be good for someone who is totally new at this? I'd appreciate any suggestions.

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  • Does Mac OS X throttle the RATE of socket creation?

    - by pbhogan
    This may seem programming related, but this is an OS question. I'm writing a small high performance daemon that takes thousands of connections per second. It's working fine on Linux (specifically Ubuntu 9.10 on EC2). On Mac OS X if I throw a few thousand connections at it (roughly about 16350) in a benchmark that simply opens a connection, does it's thing and closes the connection, then the benchmark program hangs for several seconds waiting for a socket to become available before continuing (or timing out in the process). I used both Apache Bench as well as Siege (to make sure it wasn't the benchmark application). So why/how is Mac OS X limiting the RATE at which sockets can be used, and can I stop it from doing this? Or is there something else going on? I know there is a file descriptor limit, but I'm not hitting that. There is no error on accepting a socket, it's simply hangs for a while after the first (roughly) 16000, waiting -- I assume -- for the OS to release a socket. This shouldn't happen since all prior the sockets are closed at that point. They're supposed to come available at the rate they're closed, and do on Ubuntu, but there seems to be some kind of multi (5-10?) second delay on Mac OS X. I tried tweaking with ulimit every-which-way. Nada.

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  • Does Mac OS X throttle the RATE of socket creation?

    - by pbhogan
    This may seem programming related, but this is an OS question. I'm writing a small high performance daemon that takes thousands of connections per second. It's working fine on Linux (specifically Ubuntu 9.10 on EC2). On Mac OS X if I throw a few thousand connections at it (roughly about 16350) in a benchmark that simply opens a connection, does it's thing and closes the connection, then the benchmark program hangs for several seconds waiting for a socket to become available before continuing (or timing out in the process). I used both Apache Bench as well as Siege (to make sure it wasn't the benchmark application). So why/how is Mac OS X limiting the RATE at which sockets can be used, and can I stop it from doing this? Or is there something else going on? I know there is a file descriptor limit, but I'm not hitting that. There is no error on accepting a socket, it's simply hangs for a while after the first (roughly) 16000, waiting -- I assume -- for the OS to release a socket. This shouldn't happen since all prior the sockets are closed at that point. They're supposed to come available at the rate they're closed, and do on Ubuntu, but there seems to be some kind of multi (5-10?) second delay on Mac OS X. I tried tweaking with ulimit every-which-way. Nada.

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  • Windows Server 2008 Alerting to Low memory

    - by t1nt1n
    I have a file and print server running on Windows 2008 R2 fully patched in a VSphere environment (ESXi 5.1 fully updated). Every evening between 19:20 and 19:30 our monitoring software reported that the available memory is 1% and performance is dire. There is nothing in the event logs to point to an issue. At this point in the evening I am general the only user on the system to check to see why these alerts are going off. Things I have done; Checked to see if any backups are running – None at all. Checked Scheduled tasks – None before or during this time period. Moved the VM to another host. AV is disabled to rule out that as the issue. The server does not have any problems during the day with memory when fully loaded with about 50 users. The server did have 4GB ram provisioned but I have increased this to 5Gb. Running PrefMon at the time (I will save the graphs tonight) There very little CPU usage at the time but RAM usage goes up.

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  • 20 1TB drives vs. 10 2TB drives in RAID5/6 server

    - by Hunter
    Hi everyone, I will be setting up a server at work and I need some advice on some details. The setup will be one blade-type server (8-core, 16GB RAM) with two subsystems - one for the main storage the other to back it up. I'm shooting for a 20TB array (I know it'll be less after formatting and parity drives). So is there any advantage one way or the other with either 20 1TB drives or 10 2TB drives? I'm not sure right now how many controllers I should have either (in the quote I have is a dual-port controller). I would think two controllers for a server of this size would be a better choice than the dual-port controller (but I really don't know). And would an array of this size have any performance issues in RAID 5 or 6 (I know RAID 5 or 6 are "slower" because of all the parity calculations). Also, these will be either WD RE3 (1TB) or the RE4 (2TB). Oh, also, for the backup array would it be ok to use the WD 2TB green drives (also in RAID5 or 6)?

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  • ZFS & Deduplicating FLAC Data

    - by jasongullickson
    I'm experimenting with using ZFS to deduplicate a large library of FLAC files. The purpose of this is twofold: Reduce storage utilization Reduce bandwidth needed to sync the library with cloud storage Many of these files are of the same music tracks but from different physical media. This means that for the most part they are the same and usually close to the same size, which makes me think that they should benefit from block-level deduplication. However in my testing I'm not seeing good results. When I create a pool and add three of these tracks (identical songs from different source media) zpool list reports 1.00 dedupe. If I copy all of the files (make exact duplicates of the three) dedupe climbs, so I know that it is enabled and functioning, but it's not finding any duplication in the original collection of files. My first thought was that perhaps some of the variable header data (metadata tags, etc.) might be mis-aligning the bulk of the data in these files (the audio frames) but even making the header data consistent across the three files doesn't seem to have any impact on deduplication. I'm considering taking alternate routes (testing other dedupe filesystems as well as some custom code) but since we're already using ZFS and I like the ZFS replication options, I'd prefer to use ZFS dedupe for this project; but perhaps it's simply not capable of working well with this sort of data. Any feedback regarding tuning that might improve dedupe performance for this sort of dataset, or confirmation that ZFS dedupe is not the right tool for this job are appreciated.

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  • how to build network across buildings ?

    - by Omie
    Hi ! I need some help in building a network between hundreds of computers spread across multiple buildings of my college. Yes, I'll be doing this as a part of my college project. Please see this image, it will give you enough idea of what I'm trying to achieve. http://i.imgur.com/rOohx.png All the computers in all buildings should be able to connect server. Once network is up, there will be a set of services over intranet and network use will be moderate. well, say there will be an email server and a http server. My point is, I cannot afford much of performance loss. It feels easy to connect computers inside 1 building to each other, however, I'm clueless as to how to connect all of them to server. I mean, just 1 cable won't be enough to connect 1 building to server, right ? How should I go with it ? I am not expecting detailed configuration. Just heads up will do :) Thanks

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  • How many guesses per second are possible against an encrypted disk? [closed]

    - by HappyDeveloper
    I understand that guesses per second depends on the hardware and the encryption algorithm, so I don't expect an absolute number as answer. For example, with an average machine you can make a lot (thousands?) of guesses per second for a hash created with a single md5 round, because md5 is fast, making brute force and dictionary attacks a real danger for most passwords. But if instead you use bcrypt with enough rounds, you can slow the attack down to 1 guess per second, for example. 1) So how does disk encryption usually work? This is how I imagine it, tell me if it is close to reality: When I enter the passphrase, it is hashed with a slow algorithm to generate a key (always the same?). Because this is slow, brute force is not a good approach to break it. Then, with the generated key, the disk is unencrypted on the fly very fast, so there is not a significant performance lose. 2) How can I test this with my own machine? I want to calculate the guesses per second my machine can make. 3) How many guesses per second are possible against an encrypted disk with the fastest PC ever so far?

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  • 2.6.9 Kernel on virtual server (non upgradable) - any expected problems?

    - by chris_l
    Hi, I'm considering to rent a virtual server (for me personally). The product I'm currently looking at offers IMO fair pricing, very good hardware etc. The only problem is, that I won't be able to do an upgrade to a newer kernel than 2.6.9 (running Debian Etch). Also, I can't install my own kernel modules. (The server runs with Virtuozzo, so as far as I understand it, it just does some chroot instead of a real virtualization (?)) I want to run GlassFish, Postgres, Subversion, Trac and maybe some other things on it. It will also have to employ a firewall, and provide OpenSSL for https. Ideally, it would also be able to do AIO (asynchronous IO), which could speed up some server I/O. Should I expect problems with that old kernel version, in conjunction with the software I want to install (I'd like to use current versions of the software)? One thing I already found out, is that you can't do everything with iptables, since some kernel modules are missing/things are not build into the kernel. GlassFish v3 appears to run fine at first glance. I was able to test the server for a few hours. Installing my whole setup wasn't feasible in that time, but what I can say is, that it's amazingly fast for an entry-level vserver, especially hard disk and network performance (averaging at ca. 400MBit/s). So if the kernel won't be a problem, I'd really like to take it. Thanks, Chris PS Exact kernel version: 2.6.9-023stab051.3-smp

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