[ovirt-users] oVirt 3.6 disk speeds

[Julian De Marchi]

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