[ovirt-users] [SOLVED] Re: oVirt 3.6 disk speeds

[Julian De Marchi]

heya--

Issue came down to memory. The engine had 4095MB while my test VM had 
1048MB. Bumping up memory on my test VM saw speeds increase. In any 
case, 48 - 60MBs is my real speed. Time for iozone.

Hopefully this helps others.

--julian

On 23/10/2015 1:55 PM, Julian De Marchi wrote:
> heya--
>
> Playing around with oVirt 3.6 on some new kit before I rack and stack in
> the DC.
>
>    - Dell Eql PS4210(Raid-6)
>    - Dell R630
>    - Dell N400 10GB switch
>
> I have my 10GB interfaces bonded and in a port-channel. I have setup a
> basic 3.6 oVirt self-hosted stack.
>
> I am seeing some pretty big differences in disks speeds from the
> self-hosted engine and a VM guest. Both are direct luns via iscsi from
> the SAN on the 10GB port-channel. Normal network traffic does not go
> over the 10GB.
>
> On the engine I'm seeing this:
>
> # dd if=/dev/zero of=~/testfile bs=1G count=1 oflag=dsync
> 1+0 records in
> 1+0 records out
> 1073741824 bytes (1.1 GB) copied, 1.58877 s, 676 MB/s
>
> On a test VM I'm seeing this:
>
> # dd if=/dev/zero of=~/testfile bs=1G count=1 oflag=dsync
> 1+0 records in
> 1+0 records out
> 1073741824 bytes (1.1 GB) copied, 22.0732 s, 48.6 MB/s
>
> I have played with the disk drivers for my guest VM, changing between
> drivers does not change the speed at all.
>
> What ideas do you folks have for me to narrow down this slow down? I
> don't really know where to start with this one. I also noticed that 3.6
> does not yet have ovirt-guest-agent available.
>
> I know DD is not the best test for disk speeds, but it works for what I
> need right now, iozone will be next when I'm happy.
>
> Many thanks!
>
> --julian
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