Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have HP SC08Ge HBAs and P2000 G3 solution (RAID6, 8+2 spare disks) working on XenServer 5.6.0 . What seems to be strange, is the speed - 35MB/s maximum in one VM (Squeeze). Is it normal or I have to investigate some bottleneck or whatever ... I'm quite disappointed about this controllers as they and HBAs have 6Gb/s throughput theoretically. Originally I wanted to go for iSCSI solution...argh..

EDIT: May the cables be the problem? I have not bought the original HP cables, but some Delock ones..

share|improve this question
inside VM - 35MB/s, outside VM in Dom0 it's 100MB/s. Testing with "hdparm -t /dev/xvda" in VM, and "hdparm -t /dev/sdc" in Dom0. – John Apr 19 '11 at 14:47
up vote 2 down vote accepted

That card has a PCIe x8 connector and 2 x quad 3GBps external links (not 6Gbps sorry) - of which you'll only be using one link of course but still 12Gbps should suffice. Also the chassis and disk layout is plenty quick enough to do better than the 35MBps you're seeing, even with a single disk let alone with them laid out as you have. Therefore I suspect the issue is with the OS/filesystem/hypervisor/VM stack. Have you tested the disk from the bare host OS using something like iozone? If not then I would, shutdown all extranious services first and benchmark the bare OS speed, if there's a significant difference between this and the VM then it's a hypervisor issue, if it's slow with just the base OS then perhaps you have a driver or hardware probem - at least you'll know.

share|improve this answer
Chopper3 you're my idol! :) Every answer is tip-top. The problem was in hypervisor, I reinstalled Dom0 to XenServer5.6.0fp1 and now 600MB/s inside VM :) – John Apr 26 '11 at 19:33
Yeah, brilliant aren't I ;) glad to help dude. – Chopper3 Apr 26 '11 at 20:00

I'm not sure exactly how fast that controller/disk combo should be, and while RAID6 won't help the performance I think you can safely expect more throughput than you're getting.

That said, I'd look at the VM config before the storage, most virtualisation solutions need paravirtualised drivers installed to achieve really decent IO on disk and network devices - have you installed XenServer Tools?

share|improve this answer
See my comment. 100MB/s is in Dom0, I expected better performance .. – John Apr 19 '11 at 14:48

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.