6:55 a.m.
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
7:28 a.m.
New subject: [SOLVED] Re: oVirt 3.6 disk speeds
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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12:12 p.m.
On Fri, Oct 23, 2015 at 6:55 AM, Julian De Marchi <julian(a)jdcomputers.com.au
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
You are not using direct IO, please add relevant flag.
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.
I assume both VMs have the same image format and drivers?
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.
dd is by no means a tool for disk speeds. Specially not when you are
writing zero's. I suggest fio .
Y.
Many thanks!
--julian
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Julian De Marchi -
Yaniv Kaul