[Lustre-discuss] raid5 patches for rhel5

[Robin Humble]

On Fri, Aug 01, 2008 at 01:51:36PM -0600, Andreas Dilger wrote:
>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?

that's with 1.6.5.1 RHEL5 servers.

>> 1.6.5.1 client still perform badly for us. eg.
>Have you tried disabling the checksums?
>	lctl set_param osc.*.checksums=0

yes, checksums were disabled.

>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.

doh! yes, backwards...
that was patchless 2.6.23 clients BTW.

>> > 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.

cool - thanks!

cheers,
robin