5:30 p.m.
Nova has as default cache for disks a very safe value (I think
file=directsync or writethrough). Try to change it to writeback:
disk_cachemodes="file=writeback"
On Tue, Dec 23, 2014 at 1:13 AM, Dmitry Makovey <dmitry(a)athabascau.ca> wrote:
note that all of below applies when cirros used as guest...
On 12/22/2014 04:10 PM, Dmitry Makovey wrote:
> Hi everybody,
>
> using RDO IceHouse packages I've set up an infrastructure atop of
> RHEL6.6 and am seeing a very unpleasant performance for the storage.
>
> I've done some testing and here's what I get from the same storage: but
> different access points:
>
> cinder-volume # dd if=/dev/zero of=baloon bs=1048576 count=200
> 200+0 records in
> 200+0 records out
> 209715200 bytes (210 MB) copied, 0.162997 s, 1.3 GB/s
>
> nova-compute # dd if=/dev/zero of=baloon bs=1048576 count=200
> 200+0 records in
> 200+0 records out
> 209715200 bytes (210 MB) copied, 0.167905 s, 1.2 GB/s
>
> instance # dd if=/dev/zero of=baloon bs=1048576 count=200
> 200+0 records in
> 200+0 records out
> 209715200 bytes (210 MB) copied, 10.064 s, 20.8 MB/s
>
> A bit of explanation: in above scenario I have created LV on
> cinder-node, then mounted it locally and ran command for
> "cinder-volume". Created an iSCSI target, mounted it on nova-compute,
> and ran command there. Then, via cinder created storage volume, booted
> the OS off it, and ran test from within it... Results are just
> miserable. going from 1.2G/s down to 20M/s seems to be a big
> degradation. What should I look for? I have also tried running the same
> command within our RHEL KVM instance and got great performance.
>
> I have checked under /var/lib/nova/instances/* and libvirt.xml seems to
> indicate that virtio is being employed:
>
> <disk type="block" device="disk">
> <driver name="qemu" type="raw"
cache="none"/>
> <source
>
dev="/dev/disk/by-path/ip-192.168.46.18:3260-iscsi-iqn.2010-10.org.openstack:volume-955b25eb-bb48-43c3-a14d-222c9e8c7019-lun-1"/>
> <target bus="virtio" dev="vda"/>
> <serial>955b25eb-bb48-43c3-a14d-222c9e8c7019</serial>
> </disk>
>
> guest used - is rhel-guest-image-6.6-20140926.0.x86_64.qcow2 downloaded
> off RH site.
--
Dmitry Makovey
Web Systems Administrator
Athabasca University
(780) 675-6245
---
Confidence is what you have before you understand the problem
Woody Allen
When in trouble when in doubt run in circles scream and shout
http://www.wordwizard.com/phpbb3/viewtopic.php?f=16&t=19330
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