[Rdo-list] cinder speed (slow nova?)

[Cristian Falcas]

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 at 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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