[Lustre-discuss] raid5 patches for rhel5

[Andreas Dilger]

On Aug 01, 2008  09:38 -0400, Robin Humble wrote:
> done, and yes, performance is largely the same as RHEL4. cool!
> 
> Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine   Size:chnk K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> rhel4 oss  16G:256k 84624  99 842138 92 310044 91 77675  99 491239 96 285.8  10
> rhel5 oss  16G:256k 86085  99 827731 95 327007 97 79639 100 495487 98 456.2  18
> 
> streaming writes are down marginally on rhel5, but seeks/s are up 50%.

Good to know, thanks.

> BTW - the above is with 1.6.4.3 clients.

Is this with 1.6.5 servers or 1.6.4.3 servers?

> 1.6.5.1 client still perform badly for us. eg.

Have you tried disabling the checksums?

	lctl set_param osc.*.checksums=0

Note that 1.6.5 clients -> 1.6.5 servers with checksums enabled will perform
better than mixed client/server because 1.6.5 has a more efficient checksum
algorithm.

> Version  1.03       ------Sequential Output------ --Sequential Input- --Random-
>                     -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine   Size:chnk K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
>            16G:256k 77216  99 462659 100 296050  96 68100  81 648350  93 422.2  13
> 
> which shows better streaming writes, but ~1/2 the streaming read speed :-(

You are getting that backward... 55% of the previous write speed,
90% of the previous overwrite speed, and 130% of the previous read speed.

> > Note that there are also similar
> >performance improvements for RAID-6.
> 
> I can't see the RAID6 patches in the tree for RHEL5... am I missing
> something?

Sigh, RAID6 patches were ported to RHEL4, but not RHEL5...  I've filed
bug 16587 about that, but have no idea when it will be completed.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.