Re: RAID stripe size question

> This is a relatively low end HBA with 1 4Gb FC on it.  Max sustained
IO on it is going to be ~320MBps.  Or ~ enough for an 8 HD RAID 10 set
made of 75MBps ASTR HD's.

Looking at http://h30094.www3.hp.com/product.asp?sku=2260908&extended=1,
I notice that the controller has a Ultra160 SCSI interface which implies
that the theoretical max throughput is 160Mb/s. Ouch.

However, what's more important is the seeks/s - ~530/s on a 28 disk
array is quite lousy compared to the 1400/s on a 12 x 15Kdisk array as
mentioned by Mark here:
http://archives.postgresql.org/pgsql-performance/2006-07/msg00170.php.
Could be the disk RPM (10K vs 15K) that makes the difference here...

I will test another stripe size (128K) for the DATA lun (28 disks) to
see what difference that makes, I think I read somewhere that linux
flushes blocks of 128K at a time, so it might be worth evaluating.

/Mikael