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I have a pretty beefy Xen server (8 CPUs, 4G of RAM) running about 40 256M VPSs and I've been having issues with file IO speed. What I've found is one or two VPSs on the host can severely degrade performance for everyone with a bad script the dumps big log files or is using a lot of swap.

I can limit CPU usage by limiting them to a single virtual CPU and I can limit bandwidth with IPTABLES, but I've yet to see anything that lets me monitor or control File IO. What I'm left with is people on the host complaining about file IO problems and I have no way to see the source of the problem without shutting down the VPSs one at a time and observing the effect on a test VPS.

xm top shows memory and CPU usage, but nothing about IO. Is there any way to rate limit IO in xen? Or at least a way to monitor running VM instances and see who is causing the IO problem?

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+1 for a great question. I'd imagine they have to be able to do it, because VMware ESX(i) can set a limit for IOPS per virtual disk on a VM. –  Jed Daniels Nov 10 '10 at 2:43

1 Answer 1

Check This link

XenServer, from Citrix does have a Performance Utility :

XenServer Virtual Machine Performance Utility is a XenServer virtual machine that helps troubleshoot performance related issues, such as poor performance caused by storage I/O and network I/O. The virtual machine, built on Debian Linux, contains the following test utilities and is accessible over a Web based user interface:

Disk I/O performance utility - It can be used to conduct the following disk I/Os to measure: sequential read/writes and random read/writes with various specified block sizes.

Network I/O performance utility - It is essentially a modified version of netperf. Additional information about netperf can be found at http://www.netperf.org. Netperf runs on the back end and provides end-to-end request/response round trip latency and TCP/UDP throughput tests.

Sadly - you will need a Xen

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That looks like it would give some good diagnostics, but only appears to work with the Citrix version of Xen - not the open source version. –  John P Nov 17 '10 at 14:59
    
gotcha - did not know what version you are using. –  Glenn Kelley Nov 18 '10 at 7:22
    
I do not know of a way in the opensource version... some things are kept for the for pay product sadly .... i know painful –  Glenn Kelley Nov 18 '10 at 7:23

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