Re: Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-21 Thread Thomas Broda
On Wed, 16 Feb 2011 16:07:54 +0100, Thomas Broda tho...@bassfimass.de wrote: I will try Fedora then. I've installed Fedora 14 on the hypervisor last weekend, and the disk performance is as bad as it used to be under Centos 5.5. I think this related to the RAID controller. A Google search for

Re: Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-16 Thread Thomas Broda
On Tue, 15 Feb 2011 15:50:00 +, Stefan Hajnoczi stefa...@gmail.com wrote: On Tue, Feb 15, 2011 at 10:15 AM, Thomas Broda tho...@bassfimass.de wrote: Using O_DIRECT, performance went down to 11 MB/s on the hypervisor... Hmm...can you restate that as: host X MB/s guest Y MB/s Trying dd

Re: Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-16 Thread Stefan Hajnoczi
On Wed, Feb 16, 2011 at 12:50 PM, Thomas Broda tho...@bassfimass.de wrote: On Tue, 15 Feb 2011 15:50:00 +, Stefan Hajnoczi stefa...@gmail.com wrote: On Tue, Feb 15, 2011 at 10:15 AM, Thomas Broda tho...@bassfimass.de wrote: Using O_DIRECT, performance went down to 11 MB/s on the

Re: Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-16 Thread Thomas Broda
On Wed, 16 Feb 2011 13:11:46 +, Stefan Hajnoczi stefa...@gmail.com wrote: A number of performance improvements have been made to KVM and Centos 5.5 does not contain them because it is too old. If you want to see a more current reflection of KVM performance, you could try Fedora 14 host

Re: Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-15 Thread Stefan Hajnoczi
On Mon, Feb 14, 2011 at 6:15 PM, Thomas Broda tho...@bassfimass.de wrote: dd'ing /dev/zero to a testfile gives me a throughput of about 400MB/s when done directly on the hypervisor. If I try this from within a virtual guest, it's only 19MB/s to 24MB/s if the guest is on the LVM volume (raw

Re: Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-15 Thread Thomas Broda
On Tue, 15 Feb 2011 09:19:23 +, Stefan Hajnoczi stefa...@gmail.com wrote: Did you run dd with O_DIRECT? dd if=/dev/zero of=path-to-device oflag=direct bs=64k Using O_DIRECT, performance went down to 11 MB/s on the hypervisor... -- Thomas -- ICQ: 7122237 Jabber:

Re: Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-15 Thread Stefan Hajnoczi
On Tue, Feb 15, 2011 at 10:15 AM, Thomas Broda tho...@bassfimass.de wrote: On Tue, 15 Feb 2011 09:19:23 +, Stefan Hajnoczi stefa...@gmail.com wrote: Did you run dd with O_DIRECT? dd if=/dev/zero of=path-to-device oflag=direct bs=64k Using O_DIRECT, performance went down to 11 MB/s on

Slow disk IO on virtio kvm guests with Centos 5.5 as hypervisor

2011-02-14 Thread Thomas Broda
Hi, I've set up a KVM hypervisor for testing purposes. It's running on an AMD Quad-Core Phenom with a local RAID5 which is made of three disks connected to a hardware RAID controller. On top of this, there an LVM volume. dd'ing /dev/zero to a testfile gives me a throughput of about 400MB/s