HAST performance overheads?

[Laurence Gill]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Sun, 27 Jan 2013 14:48:46 +0100
Pawel Jakub Dawidek <pjd at FreeBSD.org> wrote:

> 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.
> 

Thanks for the reply.  I'm using FreeBSD 9.1-RELEASE. Here are the
results:

 # dd if=/dev/zero of=/dev/da0 bs=1m count=10240
 10737418240 bytes transferred in 755.144644 secs (14219022 bytes/sec)

 # dd if=/dev/zero of=/dev/hast/disk0 bs=1m count=10240
 10737418240 bytes transferred in 844.167602 secs (12719534 bytes/sec)


Which indicates a very small overhead, hmmm...


- -- 
Laurence Gill

f: 08721 157 665
skype: laurencegg
e: laurencesgill at googlemail.com
PGP on Key Servers
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.19 (GNU/Linux)

iEYEARECAAYFAlEGaH4ACgkQygVt8Sq0Pf8QaQCfX4/SAGnwYXfCxJ+FFnE1OiRv
R3MAn22bxjhXnCO5Aqsx74Gxq5ZemUjX
=7dgR
-----END PGP SIGNATURE-----