[Lustre-discuss] Lustre IOkit newbie: sgpdd-survey

[Andreas Dilger]

On Jul 24, 2008  14:52 -0400, Ms. Megan Larko wrote:
> Okay.   So I have a JBOD with 16 1Tb Hitachi Ultrastar sATA drives in
> it connected to the OSS via an LSI 8888ELP controller card (with
> Battery Back-up).  The JBOD is passed to the OSS as raw space.  My
> partitions cannot exceed 8Tb, but splitting into two 7Tb will hurt
> performance....

The ideal layout would be to have two RAID-5 arrays with 8 data + 1 parity
disks using 64kB or 128kB RAID chunk size, but you are short two disks...

You may also consider using RAID-6 with 6 data + 2 parity disks.  Having
the RAID stripe width be 15+1 is probably quite bad because a single
1MB RPC will always need to recalculate the parity for that IO.

> What do I do for Lustre set-up?  I thought the fewer partitions the
> better because one does has less "overhead" space.  Do I put them out
> as 16 single Tb partitions?????   That seems like extra work for a
> file system to track.

Please see section 10.1 in the Lustre manual for more tips:
http://manual.lustre.org/manual/LustreManual16_HTML/RAID.html

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