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• How do I diagnose a bottleneck in an Intel Atom based Ubuntu server?

  - by Jon Cage

  I have a small media server at home which has software raid and a gigabit link to the rest of my network. For some reason though, I only get ~10MB/s transfers when copying to/from the server. I use software RAID5 (mdadm) over 4 1TB disks. On top of that I then use LVM to give me a huge pool of disk space which is then split up into multiple partitions which can be resized as and when they need it. I'm guessing this it most likely the cause, but I'd like to know for sure where the root cause is. So, how can I benchmark network throughput (Windows 7 desktop <- Ubuntu server) and hard disk performance to try and identify where my bottleneck might be? [Edit] If anyone's interested, the motherboard is an Intel Desktop Board D945GCLF2. So that's a 300 series Atom processor with the Intel® 945GC Express Chipset [Edit2] I feel like such a fool! I just checked my desktop and I had the slower of the two onboard NICs plugged in so the server is probably not at fault here. Transferring a copy of ubuntu off the server I get ~35-40MB/s according to Windows 7. I'll do those HD tests when I get a chance though (just for completeness).

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• Connecting to IPv6 hosts when mobile and on a Surface?

  - by Cerebrate

  Specifically, at my usual location, I have an IPv6 network which connects to the Internet via a static tunnel set up to Hurricane Electric's tunnel broker ( http://www.tunnelbroker.net/ ). This works essentially perfectly, allowing inbound and outbound connectivity. Now, however, I need to connect back to host(s) on that network over IPv6 from mobile tablet(s); meaning the conditions are such that there is no guarantee or even likelihood of native IPv6 support where it happens to be at any given time, and the IPv4 address of the tablet will change on a fairly regular basis. The native Teredo support, as configured by default, functions well enough to let me ping my target hosts, but appears to have neither the reliability nor the throughput to support anything else; I have been unable to make any actual connections (trying a number of TCP-based protocols) using it. I had considered setting up an independent tunnel for the tablet(s), and using scripts to update the client endpoint IP address when it changes, but since both (a) many of the locations will be behind NAT devices over which I have no control, and (b) the option over which I do have control is an AT&T Unite hotspot which does not offer protocol 41 forwarding or respond to ICMP on its public address, this approach does not seem viable. I am additionally constrained as the mobile tablet(s) in question are Surface RTs, and as such are incapable of running, for example, AICCU client software. What is my best option to pursue to obtain IPv6 connectivity in this scenario?

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• Can I have 2Gbit over 1Gbit Nics

  - by Daniel

  So this really baffles me. Apparently because 1Gbit can transmit data in both directions simultaneously it should be possible to get 2Gbit of data transfer on a single NIC (1Gbit flow seend and 1Gbit receive). People claim that because 1Gbit is full-duplex (almost always) it is exactly 2Gbit in total. My intuition and electrical background tells me that something is not right here 4 twisted pairs 250Mbit capacity each gives 1Gbit. Unless it is really possible to transfer data in both directions simultaneously. I did a test with iperf. Ubuntu server 12.04 <-- MacBook Pro. Both with decent CPU speed. Tested speed of connection individually and on Mac I can see 112MB/s regardless which direction data is going. On Ubuntu with vnstat and ifstat I got 970Mbit speeds. Now, launching iperf in server mode on both machines at the same time and sending data using 2 iperf clients shows that I'm for example on Ubuntu box sending at 600Mbit, and receiving 350Mbit. which adds up to pretty much 1Gbit link. So to me there is no magical 2Gbit. Can someone confirm that or tell why I'm wrong? Another thing that confuses me i the fact that e.g. 24-port switch has for example: Throughput»up»to:»50.6Mpps Switching»capacity:»68Gbps Switch»fabric»speed:»88Gbps Which would suggest thay can handle 2GBit per port.

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• repair partition table

  - by m.sr

  Hallo. I've just overwritten my partition table of my system's hard disk. i made a cfdisk on the wrong device (/dev/sda instead of /dev/sdd), deleted all partitions, made one new primary spanning over the whole device, set its type to 07 (NTFS) and hit write. So here i am with my system running. Until i reboot, i hope/guess nothing will change - meaning: all my data is accessible (I'm currently making a dd-backup of the whole device and plan to make a .tar.gz-backup of the most important data later). I also backed up /proc/partitions, /proc/diskstats (even though i guess this is more about throughput and stuff like this ...) and /sys/block/sda/sda?/{start,size}. Some further things i know: 4 primary partitions 1st partition: ~100Mb, ext3, /boot 2nd partition: ~100Mb, "Win7 Boot Partition", ntfs(?) 3rd partition: ~20...30GB, Win7, ntfs 4th partition: ~20...30GB, luks-encrypted device The luks- de crypted device is a LVM-PV The /, /home & swap-partitions are all LVs on the (VG on the) above noted PV So my questions: What is the simplest way to just write the kernels partition table to the disk? What is the simplest way to take the above mentioned (and perhaps other I don't know of ...) data and generate the partition table? Are there any problems to take care of regarding to luks and/or lvm? Is there any data I should backup before rebooting (meanig stuff from kernel [ /sys/..., /proc/...] and so on, which could help me regenerate the partition table)? Thanks a lot! P.S.: debian sid, Kernel 2.6.34-1-amd64 from debian-experimental, 80GB Intel SSD

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• Creating basic, redundant gigE or IB storage network for Xen?

  - by StaringSkyward

  With only a modest budget, I want to move my 4 xen servers over to network storage -either NFS or iSCSI which will be determined based on how well it performs when we test it (we need good throughput and it must continue to work through link and switch failure tests). We may add another couple of xen servers at some point when this is done. I don't know much about the design and operation of storage networks, so would really appreciate some hints from those with experience. The budget is around $3,800 excluding the storage appliance. I am currently thinking these are my options to remain on budget: 1) Go for used infiniband hardware and aim for 10gb performance. 2) Stick with gig ethernet and buy some new switches (cisco or procurve) to create a storage-only ethernet LAN. Upgrade to 10gigE later but try to use hardware capable of it where possible to reduce upgrade costs. I have seen used, warrantied infiniband switches at reasonable prices (presumably because big companies are converging on 10gbit ethernet?) and the promise of cheap 10gb is attractive. I know nothing about IB, so here come the questions: Can I buy 2 x switches and have multiple HBAs in my xen and storage nodes to get redundancy and increased performance without complexity or expensive management software costs? If so, can you point me to some examples? Do NFS and iSCSI work just the same regardless? Is IB a sensible choice or could/should I use ethernet or FC on the same budget - I'm keen not to get boxed into a corner for future upgrades, however. For the storage I am likely to build a storage server using nexentastor with the intention that I can later add more disks, SSDs and add another server to provide a failover option at the storage level. An HP LeftHand starter SAN is also under consideration, too. Thanks in advance.

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• Multicast image restoration with adaptive speed

  - by Clinton Blackmore

  I'm curious to know if there are any tools for restoring disk images (or even transferring files) via multicast -- for any platform, especially if the project has source available -- where the multicast rate adjusts itself on the fly. On the Mac, all multicast solutions I am aware of (such as Deploy Studio, and NetRestore before it) make use of multicast ASR (apple software restore), which has one glaring deficiency -- you have to set the multicast speed before you start sending a disk image over the network, and that speed is locked in. Either your clients can keep up and restore, or they can't*. It seems to me that it must be possible for the multicast server to adjust the data rate, so you basically say "start sending this image", clients connect, and, if they can't keep up, they tell the server so it slows down. (Likewise, I'd expect the server to try speeding up if no client is having difficulties keeping up, and I'd expect to be able to cap that maximum throughput so that other network activities can go on without being resource starved.) So, what sort of tools are out there? For Linux? Windows? Is there something for the Mac I've overlooked. [It just kills me that it is true that, by the time you get multicast up and going at a good speed to restore a lab, you could've unicasted the data to all the computers and be done.] * There is a little leeway involved. I think individual clients can say, "I missed a little bit of data" and get it, and they can opt to listen in the next time the image is sent over the network, but on the whole, if they missed it the first go round, you have to image the machine again, and there is no time savings.

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• Setting my NIC to full duplex

  - by David

  I am trying to optimize the network speed of my Solaris X86 server, and have discovered that the Cisco 3548 that it is connected to has issues with the NIC in my server. The NIC appears to have not been configured fully, and is coming up 100 half-duplex. The 3548 ports are all set to 100 full. Ideally I'd like to have the server set for 100 full, and have been attempting to configure it using ndd commands. However I have had no results. The following command: -bash-3.00# dladm show-dev rtls0 link: unknown speed: 100 Mbps duplex: unknown The NIC shows up as: pci bus 0x0001 cardnum 0x06 function 0x00: vendor 0x10ec device 0x8139 Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ which should be configurable. I have modified the configuration file from auto config (5) to 100 fdx (4) to no avail. If there is no other choice, I could alter the Cisco 3548 to be 100 half-duplex. However, this solution causes huge performance loss. Currently throughput is about 500Kbps, when it should be around 40Mbps.

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• Linux Tuning for High Traffic JBoss Server with LDAP Binds

  - by Levi Stanley

  I'm configuring a high traffic Linux server (RedHat) and running into a limit I haven't been able to track down. I need to be able to handle sustained 300 requests per second throughput using Nginx and JBoss. The point of this server is to run checks on a user's account when that user signs in. Each request goes through Nginx to JBoss (specifically Torquebox with JBoss A7 with a Sinatra app) and then makes an LDAP request to bind that user and retrieve several attributes. It is during the bind that these errors occur. I'm able to reproduce this going directly to JBoss, so that rules out Nginx at least. I get a variety of error messages, though oddly JBoss stopped writing to the log file recently. It used to report errors about creating native threads. Now I just see "java.net.SocketException: Connection reset" and "org.apache.http.conn.HttpHostConnectException: Connection to http://my.awesome.server:8080 refused" as responses in jmeter. To the best of my knowledge, I have plenty of available file handles, processes, sockets, and ports, yet the issue persists. Unfortunately, I have very little experience tuning servers. I've found a couple useful documents - Ipsysctl tutorial 1.0.4 and Linux Tuning - but those documents are a bit over my head (and just entering the the configuration described in Linux Tuning doesn't fix my issue. Here are the configuration changes I've tried (webproxy is the user that runs Nginx and JBoss): /etc/security/limits.conf webproxy soft nofile 65536 webproxy hard nofile 65536 webproxy soft nproc 65536 webproxy hard nproc 65536 root soft nofile 65536 root hard nofile 65536 root soft nproc 65536 root hard nofile 65536 First attempt /etc/sysctl.conf sysctl net.core.somaxconn = 8192 sysctl net.ipv4.ip_local_port_range = 32768 65535 sysctl net.ipv4.tcp_fin_timeout = 15 sysctl net.ipv4.tcp_keepalive_time = 1800 sysctl net.ipv4.tcp_keepalive_intvl = 35 sysctl net.ipv4.tcp_tw_recycle = 1 sysctl net.ipv4.tcp_tw_reuse = 1 Second attempt /etc/sysctl.conf net.core.rmem_max = 16777216 net.core.wmem_max = 16777216 net.ipv4.tcp_rmem = 4096 87380 16777216 net.ipv4.tcp_wmem = 4096 65536 16777216 net.core.netdev_max_backlog = 30000 net.ipv4.tcp_congestion_control=htcp net.ipv4.tcp_mtu_probing=1 Any ideas what might be happening here? Or better yet, are there some good documentation resources designed for beginners?

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• Four disks - RAID 10 or two mirrored pairs?

  - by ewwhite

  I have this discussion with developers quite often. The context is an application running in Linux that has a medium amount of disk I/O. The servers are HP ProLiant DL3x0 G6 with four disks of equal size @ 15k rpm, backed with a P410 controller and 512MB of battery or flash-based cache. There are two schools of thought here, and I wanted some feedback... 1). I'm of the mind that it makes sense to create an array containing all four disks set up in a RAID 10 (1+0) and partition as necessary. This gives the greatest headroom for growth, has the benefit of leveraging the higher spindle count and better fault-tolerance without degradation. 2). The developers think that it's better to have multiple RAID 1 pairs. One for the OS and one for the application data, citing that the spindle separation would reduce resource contention. However, this limits throughput by halving the number of drives and in this case, the OS doesn't really do much other than regular system logging. Additionally, the fact that we have the battery RAID cache and substantial RAM seems to negate the impact of disk latency... What are your thoughts?

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• Bandwidth Suggestion

  - by Campo

  I have been asked to analyze the bandwidth usage of a company and make a recommendation for upgrading their Internet connection(s). Here is the layout 3 DLS lines so it is 3x(6 Down, 1 Up Each) into a load balancer out to the office's network. 30 VOIP phones run on a T1 (1.5 Down, 1.5 Up) The users at the company are heavily uploading. It is my suspicion that the issue in slowdown is being cause by multiple people uploading and others not being able to get requests out for even simple http requests. My initial idea is to get them a fiber line with a 10 down and 10 up. What do others think on this plan? Will that be enough to host their network traffic? What do I do about the VOIP line afterward? The fiber is expensive and I know the T1 does a great job for their VOIP so I do not want to suggest a DSL line because I know it may not be sufficient. I would also like to save them some money if I can. Maybe even get a faster fiber line and forgo the T1. Though I know their load balance/switch can only handle 20MB/S throughput. Looking for some confirmation/suggestions on my plan. I am planning on going in to get some real diagnostic numbers. Any suggestions on software to use for that? Preferably Windows software.

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• OpenVPN Server - CPU is pegged out

  - by ericl42

  Hello, I am configuring OpenVPN to act as a SSL tunnel for a remote location. I have OpenVPN1 at our current location acting as a server then OpenVPN2 at the other location that is acting as a client but is also acting as a DHCP server to machines behind it so they are basically connected to the local LAN. Everything is set up fine and I can talk from location A to location B with no problems like everyone is local. I am however having some performance issues. OpenVPN1 CPU is pegged to 100% the entire time I am copying or doing any type of activity through the tunnel. I expect some CPU usage going up but nothing like this. It's really killing my performance. OpenVPN1 is running in ESX right now with 2 gig RAM and 4 procs with unlimited bursting capacity. I am using AES-192 encryption with a 1024 key. Any idea how I can get my CPU down on OpenVPN1 and my download/upload speeds higher between the tunnel? Thanks. edit: Turning down the logging helped boost the throughput a little bit, but I am still fairly shy of where I believe I should be. Also I am still maxed out on the CPU. Does anyone have any ideas? I am really stuck on this. Thanks.

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• What is the difference between disabling hibernation and idling time for a NAS?

  - by Gary M. Mugford

  I have two D-LINK DNS-323 NAS boxes with two Seagate drives in each. The first one is about a year old, the second one about three months. The first two on Monster are each 1.5T drives while the last two on Origami are 2T drives. I have never been overly happy with the Monster drives but, outside of poor throughput on small files, they have been consistently available to all programs after I put a batch file into my startup to do a directly listing of each. I added the two new drives when I added the Origami box. But, watching the dos box that comes up, I rarely see both listed before the box disappears. Other programs, backups, Belarc, even my file browsers, seem to have a dickens of a time seeing O: and P:. Finally, I decided to go into setup and turn off hibernation. Performance HAS been better since and Belarc, for instance, now sees both drives. At the time of poking around, I noticed an Idle Time feature too. What is the difference between the two settings? And for added points, how much trouble am I in for turning off hibernation? The super bonus round ... anything ELSE I should have done? Thanks in advance, GM

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• Website has become slower on a VPS, was much fast on a shared host. What's wrong?

  - by Arpit Tambi

  My shared host suspended my website stating system overload, so I moved my website to a VPS which has 4GB RAM. But for some reason the website has become very slow. This is the vmstat output - procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 0 3050500 0 0 0 0 0 1 0 0 0 0 100 0 0 Here's the Apache Benchmark output for a STATIC html page I ran on the server itself - Benchmarking www.ask-oracle.com (be patient)...apr_poll: The timeout specified has expired (70007) Total of 20 requests completed Update: Server Config: List item Centos 5.6 4 cores cpu 4 GB RAM LAMP stack with APC Wordpress Only one website It takes almost double time to load now, same website was much fast on shared hosting. I know I need to tweak some settings but have no clue where to start from? I have already tried to optimize apache, mysql etc. Update 2: CPU usage is low, see uptime output: 11:09:02 up 7 days, 21:26, 1 user, load average: 0.09, 0.11, 0.09 Update 3: When I load any webpage, browser shows "Waiting" for a long time and then page loads quickly. So I suspect server can accept only limited connections and holds extra connections in a waiting state. How to check this? Update 4: Following is the output on executing netperf TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost.localdomain (127.0.0.1) port 0 AF_INET Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 9615.40 [root@ip-118-139-177-244 j3ngn5ri6r01t3]# Here are the Apache MPM settings from httpd.conf, do they look okay? <IfModule worker.c> StartServers 5 MaxClients 100 MinSpareThreads 50 MaxSpareThreads 250 ThreadsPerChild 125 MaxRequestsPerChild 10000 ServerLimit 100 </IfModule>

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• iperf max udp multicast performance peaking at 10Mbit/s?

  - by Tom Frey

  I'm trying to test UDP multicast throughput via iperf but it seems like it's not sending more than 10Mbit/s from my dev machine: C:\> iperf -c 224.0.166.111 -u -T 1 -t 100 -i 1 -b 1000000000 ------------------------------------------------------------ Client connecting to 224.0.166.111, UDP port 5001 Sending 1470 byte datagrams Setting multicast TTL to 1 UDP buffer size: 8.00 KByte (default) ------------------------------------------------------------ [156] local 192.168.1.99 port 49693 connected with 224.0.166.111 port 5001 [ ID] Interval Transfer Bandwidth [156] 0.0- 1.0 sec 1.22 MBytes 10.2 Mbits/sec [156] 1.0- 2.0 sec 1.14 MBytes 9.57 Mbits/sec [156] 2.0- 3.0 sec 1.14 MBytes 9.55 Mbits/sec [156] 3.0- 4.0 sec 1.14 MBytes 9.56 Mbits/sec [156] 4.0- 5.0 sec 1.14 MBytes 9.56 Mbits/sec [156] 5.0- 6.0 sec 1.15 MBytes 9.62 Mbits/sec [156] 6.0- 7.0 sec 1.14 MBytes 9.53 Mbits/sec When I run it on another server, I'm getting ~80Mbit/s which is quite a bit better but still not anywhere near the 1Gbps limits that I should be getting? C:\> iperf -c 224.0.166.111 -u -T 1 -t 100 -i 1 -b 1000000000 ------------------------------------------------------------ Client connecting to 224.0.166.111, UDP port 5001 Sending 1470 byte datagrams Setting multicast TTL to 1 UDP buffer size: 8.00 KByte (default) ------------------------------------------------------------ [180] local 10.0.101.102 port 51559 connected with 224.0.166.111 port 5001 [ ID] Interval Transfer Bandwidth [180] 0.0- 1.0 sec 8.60 MBytes 72.1 Mbits/sec [180] 1.0- 2.0 sec 8.73 MBytes 73.2 Mbits/sec [180] 2.0- 3.0 sec 8.76 MBytes 73.5 Mbits/sec [180] 3.0- 4.0 sec 9.58 MBytes 80.3 Mbits/sec [180] 4.0- 5.0 sec 9.95 MBytes 83.4 Mbits/sec [180] 5.0- 6.0 sec 10.5 MBytes 87.9 Mbits/sec [180] 6.0- 7.0 sec 10.9 MBytes 91.1 Mbits/sec [180] 7.0- 8.0 sec 11.2 MBytes 94.0 Mbits/sec Anybody has any idea why this is not achieving close to link limits (1Gbps)? Thanks, Tom

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• Can enabling a RAID controller's writeback cache harm overall performance?

  - by Nathan O'Sullivan

  I have an 8 drive RAID 10 setup connected to an Adaptec 5805Z, running Centos 5.5 and deadline scheduler. A basic dd read test shows 400mb/sec, and a basic dd write test shows about the same. When I run the two simultaneously, I see the read speed drop to ~5mb/sec while the write speed stays at more or less the same 400mb/sec. The output of iostat -x as you would expect, shows that very few read transactions are being executed while the disk is bombarded with writes. If i turn the controller's writeback cache off, I dont see a 50:50 split but I do see a marked improvement, somewhere around 100mb/s reads and 300mb/s writes. I've also found if I lower the nr_requests setting on the drive's queue (somewhere around 8 seems optimal) I can end up with 150mb/sec reads and 150mb/sec writes; ie. a reduction in total throughput but certainly more suitable for my workload. Is this a real phenomenon? Or is my synthetic test too simplistic? The reason this could happen seems clear enough, when the scheduler switches from reads to writes, it can run heaps of write requests because they all just land in the controllers cache but must be carried out at some point. I would guess the actual disk writes are occuring when the scheduler starts trying to perform reads again, resulting in very few read requests being executed. This seems a reasonable explanation, but it also seems like a massive drawback to using writeback cache on an system with non-trivial write loads. I've been searching for discussions around this all afternoon and found nothing. What am I missing?

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• Slow Local Network, Windows 7, Snow Leopard, WiFi/Wired

  - by WerkkreW

  Hello - I am experiencing really poor local network performance in my home. I was recently using a Linksys WRT54G Router with DD-WRT on it, and a couple comparable Linksys-G PCI cards for connectivity but decided to upgrade hoping it would help with my performance issues. The computers in my house are connected as follows: Comcast Business Class Commercial 25mbps/10mbps (Verified with SpeakEasy and Speedtest.net) D-Link DGL-4500 Wireless N Router Windows 7x64 - D-Link DWA-552 Wireless-N Windows 7x64 - D-Link DWA-552 Wireless-N Mac Mini 10.6.2 - AirPort Extreme N Playstation 3, Hard Wired Xbox 360, Hard Wired Essentially the problem is very specific. Web browsing and uploading/downloading files from the internet is fine, more than fine. But if I want to say, Stream a video from one of my Windows 7 computers to my PS3, or copy a large video file between either of the PC's or the Mac, I get a consistent 500-900Kbps throughput at the high end. If I open my network browser, or try to browse my homegroup the response time is horrible. Both of my Windows computers are showing Strong wireless signals with a connection speed of 300Mbps. I know I can never expect to achieve anything near those speeds, but 500Kbps? Here is what I have tried so far: Enabled Single mode N-only and N/G Only on router WPA2 with AES Encrpytion Disabled "Remote Differential Compression" in Windows 7 Disabled TCP "Auto-Tuning" Used other software for file copies such as "Teracopy" I am at the end of my rope. Unfortunately I live in a 75 year old home with plaster walls, so hard-wiring my entire house isn't really an option I can handle right now. Any ideas to help me get decent speed when transferring files across my network would be greatly appreciated.

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• What is the peak theoretical WiFi G user density? [closed]

  - by Bigbio2002

  I've seen a few WiFi capacity planning questions, and this one is related, but hopefully different enough not to be closed. Also, this is related specifically to 802.11g, but a similar question could be made for N. In order to squeeze more WiFi users into a space, the transmit power on the APs need to be reduced and the APs squeezed closer together. My question is, how far can you practically take this before the network becomes unusable? There will come a point where the transmit power is so weak that nobody will actually be able to pick up a connection, or be constantly roaming to/from APs spaced a few feet apart as they walk around. There are also only 3 available channels to use as well, which is a factor to consider. After determining the peak AP density, then multiply by users-per-AP, which should be easier to find out. After factoring all of this in and running some back-of-the-envelope calculations, I'd like to be able to get a figure of "XX users per 10ft^2" or something. This can be considered the physical limit of WiFi, and will keep people from asking about getting 3,000 people in a ballroom conference on WiFi. Can anyone with WiFi experience chime in, or better yet, provide some calculations for a more accurate figure? Assumptions: Let's assume an ideal environment with no reflection (think of a big, square, open room, with the APs spaced out on a plane), APs are placed on the ceiling so humans won't absorb the waves, and the only interference are from the APs themselves and the devices. As for what devices specifically, that's irrelevant for the first point of the question (AP density, so only channel and transmit power should matter). User experience: Wikipedia states that Wireless G has about 22Mbps maximum effective throughput, or about 2.75MB/s. For the purpose of this question, anything below 100KB/s per user can be deemed to be a poor user experience. As for roaming, I'll assume the user is standing in the same place, so hopefully that will be a non-issue.

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• Network speed between a VM and another machine which is not residing on the same host, is 11MB/s at most

  - by Henno

  Problem Network speed between a VM and another machine which is not residing on the same host, is 11MB/s at most. Topology Facts ESXi5 version is 5.0.0.504890 VM has the latest Vmware Tools installed VM is using E1000 network driver Physical box has Win Srv 2008 R2 as the OS CrystalDiskMark says the drive on physical box can read/write 100MB/s vCenter is another vm on esx both vm and physical box are showing 1Gbps link speed Configuration Networking shows vmnic0 as 1000 Full NTttcp is a client/server tool from Microsoft for measuring pure network throughput Here's what I've done so far: Test1: VM is running Filezilla FTP Server (default settings, one user account made) Physical box is running Filezilla FTP Client (default settings) Physical box is uploading a big file to FTP server Transfer speed (as observed by Windows Task Manager on both machines): ~11MB/s (bad) Physical box is downloading that file from FTP server Transfer speed (as observed by Windows Task Manager on both machines): still ~11MB/s (bad) Could it be disk performance issue? Test2: Physical box is running ntttcpr.exe -a 6 -m 6,0,VM_IP_ADDRESS VM is running ntttcps.exe -a 6 -m 6,0,PHY_BOX_IP_ADDRESS Transfer speed (as observed by Windows Task Manager on both machines): ~11MB/s (bad) Could it be switch performance issue? Test3: physical box is running vSphere Client I open Summary Storage datastore Browse Datastore... from physical box and upload a file to datastore Transfer speed (as observed by Windows Task Manager on physical box): ~26-36MB/s (good) Could it be a vm specific issue? Test4: Installed ntttcp to another vm on the same esx server Measured network performance between vms on the same esx server with NTttcp Transfer speed (as observed by Windows Task Manager on physical box): ~90-120MB/s (excellent :) Test5: I have another esx server on the same site, connecting to the same datastore and same switch. Those two ESX servers have both 2 NICs. One NIC goes to switch while the other goes directly to the other ESX server. vMotioned one of the testing vms off to the other ESX host Measured network performance between vms on different esx servers with NTttcp Transfer speed (as observed by Windows Task Manager on physical box): ~11MB/s (bad) While I'm aware of these: ESXi 4.1 slow file transfer ESXi 5 network performance is slow Debian Etch and ESXi slow network speeds VMWare ESXi slow file copy to guest they did not help (or I must have been missed something)

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• Time-Machine backup over SSH tunnel to NFS mount

  - by BTZ

  I've recently started using a new NAS which runs CentOS 6.2. One of the purposes of the NAS would be to serve as a backup target. Whilst I have been using Apple's Time-Machine for a while and I am very satisfied with it, I'd like to continue using it. Backing up directly to an address in my network is no hassle; all works fine. For security reasons I'd like all my traffic to go through an ssh tunnel to the NAS. This way I can avoid needing to get a VPNserver (for personal reasons). As of NFSv4 the NFS deamon is bound to port 2049, which makes it easy for me to direct all traffic through a ssh tunnel. Tunnel: ssh -f admin@ms -L 2000:localhost:2049 -N Mount: mount -t nfs -o nfsvers=4,rw,proto=tcp,sync,intr,hard,timeo=600,retrans=10,wsize=32768,rsize=32768,port=2000 localhost:/mac_backup /Volumes/backup This works fine for Finder/terminal and throughput is almost equal to direct traffic. (CPU of the NAS does ride high when I reach max bandwidth though) Now the problem: With Time-Machine I can't use the NFS mount point mounted on localhost. TM seems to try to connect to it and then give me a "OSStatus error 65". I also tried using NFSv3 (I correctly forwarded all ports) with no luck. Can anyone shed a light on this and/or give a solution?

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• TCP Server Memory management: #Connections Vs. #Requests

  - by Andrew

  Given that, there is no theoretical limit to number of concurrent TCP connections a Windows 2008 server can handle. Only thing will happen is, with each connection there will be memory consumption in server. Unfortunately, memory is not unlimited (and I want to utilize only physical memory). For example, lets say we've 2GB server memory. Now there are two extreme cases: Case 1: If we've allocated 64KB buffer for each connection (only to receive incoming request), then 32768 connections can consume all the 2GB of memory. This will not leave any memory to queue/process incoming requests from those connections. Case 2: On the other hand, lets say a single (or very few) connections continuously keeps sending request buffers (for example, video streaming from one connection to other) and server cannot process them within time, those buffers will get piled up in server and eventually will occupy most of the servers memory. And it will not leave any memory for new connection thereafter. This is the real dilemma in server design bugging me badly for last many days. If I can decide on max size of request buffer per connection and max number of requests to allow in queue per connection. Then, based on available server memory, it will then automatically set limit on max number of concurrent connections. How to decide on these limits to achieve best performance and throughput? I am just looking for perfect utilization of server resources. Are there any standard guidelines or empirical data available with someone who can share with me please.

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• Road Warrior VPN Setup

  - by wobblycogs

  I apologise up front for the rather open ended nature of this question but I've got well out of my depth and could really do with some pointers. I need to set up a road warrior VPN solution which will allow our customers to securely access a number of services we provide for them. Customer machines will be running a variety of Windows versions from XP onwards with a variety of patch levels. Typically they will connect from the clients main offices but not always. It is safe to assume that all clients will be behind NATs but we may occasionally see a connection that isn't NAT'ed. Typical connection situation is therefore: Customer Laptop -- Router (NAT) -- Internet -- VPN Server + Firewall -- Server (Win 2008 R2, Non-routable IP) There will initially be a dozen or so people that could connect but that will grow quickly to around 100. It's unlikely that we'll see that many concurrent connections though, I imagine our total VPN throughput would be <50Mbps peak. What are my options for setting this up? I've been trying to set up a system like this using a MikroTik router for a few days but have struggled to get it working correctly, particularly with NAT'ed clients. I've had a quick look at OpenVPN and liked what I saw but I think it's unlikely our customers IT departments would allow the client to be installed. Finally I've looked at the Cisco ASA range but I'm on a fairly tight budget so this is less preferable but it looks like it would work pretty much out of the box. My fall back position is to connect the server directly and use the provided VPN + Firewall facilities but that is far from ideal as the number of servers is likely to grow over time.

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• What performance degradation to expect with Nginx over raw Gunicorn+Gevent?

  - by bouke

  I'm trying to get a very high performing webserver setup for handling long-polling, websockets etc. I have a VM running (Rackspace) with 1GB RAM / 4 cores. I've setup a very simple gunicorn 'hello world' application with (async) gevent workers. In front of gunicorn, I put Nginx with a simple proxy to Gunicorn. Using ab, Gunicorn spits out 7700 requests/sec, where Nginx only does a 5000 request/sec. Is such a performance degradation expected? Hello world: #!/usr/bin/env python def application(environ, start_response): start_response("200 OK", [("Content-type", "text/plain")]) return [ "Hello World!" ] Gunicorn: gunicorn -w8 -k gevent --keep-alive 60 application:application Nginx (stripped): user www-data; worker_processes 4; pid /var/run/nginx.pid; events { worker_connections 768; } http { sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 65; types_hash_max_size 2048; upstream app_server { server 127.0.0.1:8000 fail_timeout=0; } server { listen 8080 default; keepalive_timeout 5; root /home/app/app/static; location / { proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect off; proxy_pass http://app_server; } } } Benchmark: (results: nginx TCP, nginx UNIX, gunicorn) ab -c 32 -n 12000 -k http://localhost:[8000|8080]/ Running gunicorn over a unix socket gives somewhat higher throughput (5500 r/s), but it still does't match raw gunicorn's performance.

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• Slow Local Network, Windows 7, Snow Leopard, WiFi/Wired

  - by WerkkreW

  I am experiencing really poor local network performance in my home. I was recently using a Linksys WRT54G Router with DD-WRT on it, and a couple comparable Linksys-G PCI cards for connectivity but decided to upgrade hoping it would help with my performance issues. The computers in my house are connected as follows: Comcast Business Class Commercial 25mbps/10mbps (Verified) D-Link DGL-4500 Wireless N Router Windows 7x64 - D-Link DWA-552 Wireless-N Windows 7x64 - D-Link DWA-552 Wireless-N Mac Mini 10.6.2 - AirPort Extreme N Playstation 3, Hard Wired Xbox 360, Hard Wired Essentially the problem is very specific. Web browsing and uploading/downloading files from the internet is fine, more than fine. But if I want to say, Stream a video from one of my Windows 7 computers to my PS3, or copy a large video file between either of the PC's or the Mac, I get a consistent 500-900Kbps throughput at the high end. If I open my network browser, or try to browse my homegroup the response time is horrible. Both of my Windows computers are showing Strong wireless signals with a connection speed of 300Mbps. I know I can never expect to achieve anything near those speeds, but 500Kbps? Here is what I have tried so far: Enabled Single mode N-only and N/G Only on router WPA2 with AES Encrpytion Disabled "Remote Differential Compression" in Windows 7 Disabled TCP "Auto-Tuning" Used other software for file copies such as "Teracopy" I am at the end of my rope. Unfortunately I live in a 75 year old home with plaster walls, so hard-wiring my entire house isn't really an option I can handle right now. Any ideas to help me get decent speed when transferring files across my network would be greatly appreciated.

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• plesk: how to configure reverse proxy rules properly?

  - by rvdb

  I'm trying to configure reverse proxy rules in vhost.conf. I have Apache-2.2.8 on Ubuntu-8.04, monitored by Plesk-10.4.4. What I'm trying to achieve is defining a reverse proxy rule that defers all traffic to -say- http://mydomain/tomcat/ to the Tomcat server running on port 8080. I have mod_rewrite and mod_proxy loaded in Apache. As far as I understand mod_proxy docs, entering following rules in /var/www/vhosts/mydomain/conf/vhost.conf should work: <Proxy *> Order deny,allow Allow from all </Proxy> ProxyRequests off RewriteRule ^/tomcat/(.*)$ http://mydomain:8080/$1 [P] Yet, I am getting a HTTP 500: internal server error when requesting above URL. (Note: I decided to use a rewrite rule in order to at least get some information logged.) I have made mod_rewrite log extensively, and find following entries in the logs [note: due to a limitation of max. 2 URLs in posts of new users, I have modified all following URLs so that they only contain 1 slash after http:. In case you're suspecting typos: this was done on purpose): 81.241.230.23 - - [19/Mar/2012:16:42:59 +0100] [mydomain/sid#b06ab8][rid#1024af8/initial] (2) init rewrite engine with requested uri /tomcat/testApp/ 81.241.230.23 - - [19/Mar/2012:16:42:59 +0100] [mydomain/sid#b06ab8][rid#1024af8/initial] (3) applying pattern '^/tomcat/(.*)$' to uri '/tomcat/testApp/' 81.241.230.23 - - [19/Mar/2012:16:42:59 +0100] [mydomain/sid#b06ab8][rid#1024af8/initial] (2) rewrite '/tomcat/testApp/' - 'http:/mydomain:8080/testApp/' 81.241.230.23 - - [19/Mar/2012:16:42:59 +0100] [mydomain/sid#b06ab8][rid#1024af8/initial] (2) forcing proxy-throughput with http:/mydomain:8080/testApp/ 81.241.230.23 - - [19/Mar/2012:16:42:59 +0100] [mydomain/sid#b06ab8][rid#1024af8/initial] (1) go-ahead with proxy request proxy:http:/mydomain:8080/testApp/ [OK] This suggests that the rewrite and proxy part is processed ok; still the proxied request produces a 500 error. Yet: Addressing the testApp directly via http:/mydomain:8080/testApp does work. The same setup does work on my local computer. Is there something else (Plesk-related, perhaps?) I should configure? Many thanks for any pointers! Ron

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• What is the best private cloud storage setup

  - by vdrmrt

  I need to create a private cloud and I'm searching for the best setup. These are my 2 most important requirements 1. Disk and system redundant 2. Price / GB as low as possible The system is going to be used as backup setup which will receive data 24/7 over SFTP and rsync. High throughput is not that important. I'm planning to use glusterfs and consumer grade 4TB hard-drives. I have worked out 3 possible setups 3 servers with 11 4TB HDD Setup up a replica 3 glusterfs and setup each hard drive as a separate ext4 brick. Total capacity: 44TB HDD / TB ratio of 0.75 (33HDD / 44TB) 2 servers with 11 4TB HDD The 11 hard-drives are combined in a RAIDZ3 ZFS storage pool. With a replica 2 gluster setup. Total capacity: 32TB (+ zfs compression) HDD / TB ratio of 0.68 (22HDD / 32TB) 3 servers with 11 4TB consumer hard-drives Setup up a replica 3 glusterfs and setup each hard-drive as a separate zfs storage pool and export each pool as a brick. Total capacity: 32TB (+ zfs compression) HDD / TB ratio of 0.68 (22HDD / 32TB) (Cheapest) My remarks and concerns: If a hard drive fails which setup will recover the quickest? In my opinion setup 1 and 3 because there only the contents of 1 hard-drive needs to be copied over the network. Instead of setup 2 were the hard-drive needs te be reconstructed by reading the parity of all the other harddrives in the system. Will a zfs pool on 1 harddrive give me extra protection against for example bit rot? With setup 1 and 3 I can loose 2 systems and still be up and running with setup 2 I can only loose 1 system. When I use ZFS I can enable compression which will give me some extra storage.

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