Ubuntu Networking :: Long Latency On LAN Between 10.14 LTS Servers
Jun 8, 2011
we are setuping high-performance web farm with 4 ubuntu servers (all 10.14 LTS 64bit, i5Core CPU, 16GB Ram). One server is "database" server with mysql installed, three servers are "webservers" with tomcat installed. All three webservers have public IP and are connected directly to internet by eth0 (onboard network card) and are connected to switch that is connected to database server by eth1 (pci network card). All servers has stardard instalation with no special modules/programes installed.
Web servers are already under load, but only on about 10 requests/minute. After several hours in production, strange thing happened - one of the web servers (each time another one, so it is happening to all of them but not at once) starts to have pings to database (that is connected directly on LAN) = 100ms (other two servers still has like 0,02ms). Pings stay high until we do /etc/init.d/networking restart, after that it is fixed and pins are again low again. Another strange think is, that when we let ping running for some time, it is slowly dropping from 100ms to 1 ms and then again jumps to 100ms (exactly to 100ms always) and again starts dropping - so it is cycling over and over again (one cycle takes about 2 minutes).
We were trying reconfigure network, play with switch (the same situation was happening even without switch when there was only one webserver and one database server directly connected), disable IPv6 but nothing helped. The only thing that we discovered is that it has to be caused by network configuration.Do you have any idea what can cause it? We went through systems logs but found nothing suspicious (at least according to our understanding).
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Dec 15, 2010
I'm experiencing massive latency/unreachable problems on my Linux machine. It's true for all network connections, here's an example of me trying to ping my router:
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=15115 ms
64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=14107 ms
64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=13107 ms
64 bytes from 192.168.0.1: icmp_req=4 ttl=64 time=12107 ms
64 bytes from 192.168.0.1: icmp_req=5 ttl=64 time=11108 ms
[Code]...
I've tried now with both the maverick default kernel and 2.6.37-rc5 kernel (both 64 bit), same result. If I take the card up and down (ifup, ifdown) performance is restored for a little while, then it's back. I've tried changing cable, network card and router port but no luck.
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Jan 8, 2011
I just put 10.10 on my D830 and I love it except for a delay when I'm using the internet. When I click on a link while surfing the web it takes about 13 seconds before it responds. After that it works just fine.
My Windows 7 PC and my Macbook Pro don't do that so I'm guessing it has something to do with Ubuntu.
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Sep 14, 2011
I'm hoping to find an existing Linux tool for measuring latency:
I'm trying to diagnose how much latency my OS and NIC card are adding to TCP latency in Linux. I looked at the following tools but all (at least at the surface level) measured bandwidth (Mbps/sec) rather than latency (nanoseconds for transmition of 1 packet of size x).
If I were to write a custom test, it would likely do the following:
Client:
Create a fake message of the specified length with some padding for an incrementing identifier. Open a TCP connection (with the right parameters like TCP_NODELAY, etc) Loop and send messages containing an incrementing identifier. Store the current system time (in nanos) associated with the identifier. Listen for responses, record the current time and record the latency of that identifier asynchronously Server Listen for a connection Echo back any message received
Assuming both boxes had the same setup (configs, cards, OS, CPU, etc), are relatively close to eachother in the network, and one knows roughly the network's latency contribution, one could get a rough estimate of the OS + NIC contribution and begin testing various configurations.
One could also get a more accurate picture of the latency by using a network sniffer and snooping on the lines between the two hosts, calculating the latency between the two sides for an ID, and then subtracting that from the internally measured latency.
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Apr 20, 2011
I have a dedicated host on my lan to monitor other hosts/services using Nagios. I'm in the process of migrating to Zabbix on that host to perform the same purpose. Both Nagios and Zabbix monitor icmp ping latency (Nagios uses ping, Zabbix uses fping) and over time the latency to other hosts grows until threshold alarms are triggered. In one week, the average latency grows from sub-millisecond to over 100 milliseconds, and continues to grow until the Nagios host is rebooted. I have verified the latency numbers using ping/fping from the command line on the Nagios host.
The problem is that pings from the monitored hosts to the Nagios host show normal latency at the time the Nagios host is showing high latency from itself to the monitored hosts. The Nagios host and monitored hosts are all connected to the same Dell 24 port gigabit switch. I already posted this question on the Zabbix forums with a graph of the latency but there were no answers. [URL] why the icmp ping latency is growing over time and how I can fix it short of rebooting the host on a schedule.
[Code]...
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Jan 10, 2011
I have a few headless servers running in my home office and I can easily see how these machines could get lost or forgotten. Linux is such a beautiful operating system it often puzzles me why it isn't more popular. People say that Linux isn't user friendly, but honestly I think it's more user friendly than Windows. If you took two people who have never used a computer before and sat one down in front of a computer running Linux and the other person in front of a computer using Windows, I'd like to believe that the person using the Linux computer would excel much quicker.
Anyway, if you have a server running out of your home, or office, how long has your server ran without it crashing? Secondly, compare that figure against how long a computer running Microsoft has run without crashing or forcing a restart.
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Jul 5, 2011
I am following this howto to install Apache, MySQL, and PHP5:
[URL]
I have just installed Apache and I am pointing my browser to:
http://192.168.0.100
but I am getting the error message that the server is taking too long to respond.
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Jan 9, 2010
just start Ubuntu 9.04 said: File system chek failed a long is beging saved /var/long/fsck/checkfs if that location is writable Please repair the file systmen manually A maintenance shell will now be started Ctr+ D terminate this shell and resume system boot. Give root password for maintenance or type Control +D to continue. I did Ctr+D , and after login said , that can not find /home. I starte with the live cd:
[Code]....
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Apr 12, 2010
I'm running Ubuntu 9.10 on a VPS with linode.I run around 10 sites from this vps and whenever I try to do anything thats related at all to email (such as user registration, contact form submission) the process itself can take anywhere from one to five minutes. I realize that this is most likely due to a misconfiguration with how my email has been set up.
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Feb 17, 2011
I've set up a cups printing server using ubuntu 10.04.1 LTS. The printer's a HP Laser Jet 1018 I can connect to it over vpn using openvpn from my netbook which is also running ubuntu 10.04.1. I can connect to the printer all right and test page prints without a problem. But if I try to print anything else, it take at least 5 minutes before the job is successfully send and printed out.
Also, on the client side, for example, the file size would like 500k, and when it finally prints out, the file size on the server side is less than 10k. The file is a black and white document, and from what I can tell, the printed page is not missing any information.
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Oct 13, 2010
I'm trying to get granular with TCP, one of the answers I can't seem to find is. When a client server connection is lost without closing, how many duplicate ack's are sent until the session is closed. I've kind of figured out the the sender will continue to retransmit a segment for about 9 mins if not Ack'd. going from 1.5,3,6,12,24,48 and the continuing with 64 seconds up to around 9 minutes before is resets the session. but whats happening at the other end.?
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May 15, 2010
It's an eMachines T2899 desktop, FIC AU31 motherboard, nForce2 chipset, AC97 sound (integrated), running Xubuntu 10.04 (wubi install), 2.6.32-22.I've got terrible sound latency (about one second between actions and sound) in some programs.Flash in both firefox and chrome (including ..... videos) and ZSNES (SNES emulator) are two offenders, as is Audacity.Videos played in the default "movie player" and VLC play with no delay, though.I've been told it could be an issue with the ALSA buffer size, or pulseaudio introducing latency... but I've no clue how to go about fixing it.Upon using the SNES9X emulator (which allows for choice of sound system)... Portaudio causes laggy emulation and bad sound latency. Open Sound System plays fine. SDL causes laggy emulation and bad sound latency. ALSA plays fine. Pulse Audio plays fine."sudo apt-get remove --purge pulseaudio" did nothing, so I reinstalled it just in case.
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Mar 10, 2010
I was on a car trip earlier, but we were stuck in traffic. The stop-go stop-go kind of BS. I pulled out my 9.10 laptop and figured I'd scan for wifi networks and see how good America was at securing their networks. (I work in IT support so it's one of those things I preach to no end yet people rarely listen).
I was using wifi radar, and picked up a truckload of networks every time we'd stop. But something didn't sit well with me. When I click on the network manager icon in the top gnome panel to see what networks were available, it never seemed to refresh.
Example - the first 5 networks I saw were 1, 2, 3, 4, 5. We would stop-go more and more and miles later when I'd see more networks in the area show up in wifi radar, yet hit my network manager, I'd STILL see networks 1, 2, 3, 4, 5 and not 30, 31, 32, 33, etc like I expected.
What kind of refresh time or cache or whatever does network manager have? I just didn't understand why I was seeing the original networks from 15 minutes/miles ago and it never seemed to update.
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Aug 9, 2010
My problem is that every time I use the Ethernet connection (I don't have wireless card) there is a delay of around 30s, even though my download speed is not affected at all once the connection is "established" , no matter what application I use (Synaptic, ssh, firefox, google chrome,wget, update manager, etc.). A weird thing is that my ethernet connection always appears as active.
I'm sure I'm not the only one who has experienced this issue, since I've read the same problem on other forums, but no one has come up with a solution. I hope that there will be a solution at last by this time.
I've been around with this problem for about 1 month, I've tried all sorts of tweaks that involve disabling ipv6 and nothing happens. I don't really know what triggered off this issue because it all started all of a sudden and I don't remember having installed any important update by the time this happened (I did a clean installation of Ubuntu 10.04 32bits on the release date).
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Feb 8, 2010
When I turn on the computer, it connects to wireless automatically. That's good. But it doesn't stay connected very long. Especially if I turn on a p2p program or make a call through messenger. Then I get disconnected suddenly and if I want to connect again it doesn't work anymore. Network - You are now disconnected and that's it. Every time it happens I restart the system. I use an Acer Aspire 5738z laptop.
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Mar 14, 2010
I suspect this has been posted before, but I'm new enough to the OS to lack the proper vocab for a proper search.
In any case, I'm basically trying to run programs remotely at work (from home) that will run for a long time. I first ssh into the appropriate network, then ssh into the individual machine. This works great and I can run programs no problem. The issue is that these programs can run for days or weeks, and the network kicks me out after some period of time due to inactivity.
Is there a way to start a program on a remote machine then terminate the connection but have it keep running?
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Jul 27, 2010
I'm running Kubuntu 10.04 and am trying to install OpenVPN as per the instructions here:-[URL]..However, when I try enter the following I just get a continuous "string is too long, it needs to be less than 40 bytes long" message.
./pkitool --initca I've had a look around in the forum and in google and can find a reference to this problem with 9.x but from what I can see this has supposedly been fixed for v10.04. Is there some sort of workaround I can apply to get this to work?
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Jan 21, 2011
I moved my UBUNTU workstation from basement to second floor and it did not connect to my home network. When moved back to basement level, it connects. Cat5 cable to second floor is 3 time longer than one used to connect in basement, almost 100feet. My Windows XP laptop has no problem in connecting to the network on the second floor using the sane cable that was used with UBUNTU.
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Sep 4, 2010
How do I find out the memory bandwidth/latency to RAM of the machine?
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Jun 12, 2010
I'm getting close to ordering the components for a new machine based on the AMD Deneb quad core and had one last question.I'd like to try a little careful overclocking, not only for the performance increase but also to learn how. Nothing extreme, no gaming, just whatever I can get with good stability with the stock heatsink and fan.I was going to get 8GB on 2x4GB strips but they are all CAS latency 9. The MB has 4 slots for a total of 16GB capacity. Would I be better off going with 4x2GB strips and try to get a lower latency strip like maybe 7?
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Apr 26, 2010
I am having a problem with internet browsing. Whenever I type the address of any webiste like Google
or URL...or any other, the firefox gives message at "Status Bar" that "Looking up google.com" or "Looking up yahoo.com" etc for every website for about 20-25 seconds and than launches the website successfully. Why this is happening and how can I correct it?I also tried this in Opera and Google Chrome and same problem occurs in them.Moreover, if I ping any domain inside terminal, it instantly starts pinging (with ttl 51) and recieving data from that domain resulting that the problem is with browsers.
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Oct 7, 2010
I have a RHEL 4 server delivering long messages to several RHEL 4 clients. They work fine.I am trying a RHEL 5 client running the same client application as the RHEL 4 clients. The RHEL 5 client looses most messages. have tried with two other clients running CentOS 5 with similar results. The server indicates write failure or blocked. The messages are typically 50 kilobytes. I have changed many parameters in sysctl.conf Has anyone encountered similar problems?
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Oct 12, 2010
I just installed Maverick Studio on a new hard drive, and am using an NVIDIA GeForce 7300 LE GPU. If I boot into the 2.6.35-22-generic kernel, everything runs fine, but if I try to boot into either the 2.6.35-20-Low Latency, or 2.6.33-29-Realtime kernels (installed from Synaptic), the computer boots straight to a command prompt instead of the desktop. Does anybody know what causes this? I need to be able to use one of these kernels for doing music production.
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Mar 29, 2010
Brand new network, just installed, all ubuntu 9.10 boxes connected to a Dell 2206 dumb gigabit switch, and from there to Dlink router to cable modem. Pretty simple. ISP confirms great link out and inbound,
However, http requests can sit for 20-30 seconds (sometimes longer), before content returns, same for pings.
Some thought it might be MTU-related. What is best MTU setting 1500/1492/ ?
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Jan 20, 2011
When I need to type in the password to get on a wifi network, the "connect" button is grayed out and unclickable until I've typed in 8 characters for the password, making it impossible to connect to networks with shorter passwords. I'm not sure if this problem is unique to 10.10 or not, I've been using linux for a couple years now and I've never tried to connect to a network with such a short password before until last weekend, after my friend figured out how to change his password from the one his ISP set for him.
I'm running Xubuntu 10.10 on an IBM T42 laptop, here's the relevant hardware from the lspci command, 02:01.0 Ethernet controller: Intel Corporation 82540EP Gigabit Ethernet Controller (Mobile) (rev 03) 02:02.0 Network controller: Intel Corporation PRO/Wireless LAN 2100 3B Mini PCI Adapter (rev 04)
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Aug 6, 2011
I currently have a Nexxt Lynx 150 Wireless USB adapter attatched to one of my home destops to recieve my wifi signal, however, i have run into a speed bump in terms of getting it connected to my ubuntu 11.04. This adapter works perfectly in windows and on the ubuntu live cd, but, when i install ubuntu to my hard drive and try to connect to my network,
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Feb 26, 2011
As I am trying to understand if there are any advantages using a kernel optimized to have low latency for the desktop, it would very helpful if anyone using one could give me his opinion. I read about the liquorix kernel and found a controversy and used google to find more information.
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Jun 20, 2011
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Jun 28, 2011
is there a realtime or low-latency kernel in a repository somewhere for OpenSUSE 11.4? I know I can just compile a rt kernel, but that's a bit tedious and I'd like to avoid it if possible.
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Feb 17, 2011
I have a four-cores machine (core1,core2, core3, core4 ). I want to test the communication or latency between two cores (for example, core1 and core2; core3 and core4). Does anyone know how to write a code to test it under linux operating system?
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