HAST performance overheads?

[Pawel Jakub Dawidek]

On Fri, Jan 25, 2013 at 12:10:44PM +0000, Laurence Gill wrote:
> If I create ZFS raidz2 on these...
> 
>  - # zpool create pool raidz2 da0 da1 da2 da3 da4 da5
> 
> Then run a dd test, a sample output is...
> 
>  - # dd if=/dev/zero of=test.dat bs=1M count=1024
>      1073741824 bytes transferred in 7.689634 secs (139634974 bytes/sec)
> 
>  - # dd if=/dev/zero of=test.dat bs=16k count=65535
>      1073725440 bytes transferred in 1.909157 secs (562408130 bytes/sec)
> 
> This is much faster than compared to running hast, I would expect an
> overhead, but not this much.  For example:
> 
>  - # hastctl create disk0/disk1/disk2/disk3/disk4/disk5
>  - # hastctl role primary all
>  - # zpool create pool raidz2 disk0 disk1 disk2 disk3 disk4 disk5
> 
> Run a dd test, and the speed is...
> 
>  - # dd if=/dev/zero of=test.dat bs=1M count=1024
>      1073741824 bytes transferred in 40.908153 secs (26247624 bytes/sec)
> 
>  - # dd if=/dev/zero of=test.dat bs=16k count=65535
>      1073725440 bytes transferred in 42.017997 secs (25553942 bytes/sec)

Let's try to test one step at a time. Can you try to compare sequential
performance of regular disk vs. HAST with no secondary configured?

By no secondary configured I mean 'remote' set to 'none'.

Just do:

	# dd if=/dev/zero of=/dev/da0 bs=1m count=10240

then configure HAST and:

	# dd if=/dev/zero of=/dev/hast/disk0 bs=1m count=10240

Which FreeBSD version is it?

PS. Your ZFS tests are pretty meaningless, because it is possible that
    everything will end up in memory. I'm sure this is what happens in
    'bs=16k count=65535' case. Let try raw providers first.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl
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