buccy

Thanks Ric_ could you possible do one more test on a VM running on shared storage NFS or iSCSI? Cheers.

I was wondering what kind of servers, do you have any SQL or Exchange VM's? I have updated my test box to 5.6 and tested the NFS performace and there is no change unfortunately, iSCSI performace is marginally better.

cookie what type of VM's do you use? Generally the slow writes is not a real problem but on a couple of our APP servers (SQL databases) it is starting to cause problems, the main one is that it is so much slower than a physical box. I have started testing iSCSI SR's and while the read speeds are generally slower than NFS the writes are at least twice as fast, untill like you mentioned, during busy periods speeds basically halve. Ric_ have you had a chance to test your system?

iSCSI numbers would be useful also as I have begun investagating using it if I can't improve the NFS numbers. Both programs I listed just create temp files on the guest VM and are removed after the run. ATTO is lightweight and no install neccessary, so might be the best option.

Cookie any chance you could post some benchmark results from either Crystal Disk Mark or ATTO Disk benchmark, it would be reassuring to know if what I am experiencing is common so I can stop pulling my hair out!

I have done some further testing and enabled flow control on the SAN switch, this has made performance slightly worse!

I am a bit weary of upgrading to 5.6 as a number of issue's with it have been raised. I am going to setup a Openfiler box and test the performance from that, in the mean time is there anyone else who experiences slow writes in Xenserver?

Your local results sound a bit off, my workstation gets 85.2 MB/s read and 76.82 MB/s write, I get similar results to these on a VM running on local storage. Thanks for posting your results.

Yeah sorry here Crystal Dew World

Its just a quick and dirty benchmark program called crystal disk mark, but I have seen the same results using ATTO disk benchmark as well. If you could post your results that would be great.

Hi All, I know that several people on here must have a similar setup and I am wondering if they experience the same behaviour or have a fix/workaround. Here is the setup/issue: 3 Xenserver 5.5 hosts in a pool with a NFS SR hosted on the Sun 7110, when benchmarking within a guest VM Read speeds are great around 80 MB/s but write speeds are just horrible I'm lucky it I get over 10 MB/s! (see screenshot) There are numerous threads over on the Citrix forums regarding this problem but none seem to offer a solution. Is there someone out there with a similar setup that is able to test the write performace in a guest VM and post the results? Does anybody have an idea how to fix this issue? Cheers.