I have a 13 disk (250G each) software raid 5 set using 1 16 port adaptec SATA 
I am very happy with the performance. The reason I went with the 13 disk raid 5 
set was for the space NOT performance. 
  I have a single postgresql database that is over 2 TB with about 500 GB free 
on the disk.   This raid set performs
about the same as my ICP SCSI raid controller (also with raid 5).  

That said, now that postgresql 8 has tablespaces, I would NOT create 1 single 
raid 5 set, but 3 smaller sets.  I also DO
NOT have my wal and log's on this raid set, but on a  smaller 2 disk mirror.


---------- Original Message -----------
From: Greg Stark <[EMAIL PROTECTED]>
To: Alex Turner <[EMAIL PROTECTED]>
Cc: Greg Stark <[EMAIL PROTECTED]>, Arshavir Grigorian <[EMAIL PROTECTED]>,,
Sent: 14 Mar 2005 15:17:11 -0500
Subject: Re: [PERFORM] Postgres on RAID5

> Alex Turner <[EMAIL PROTECTED]> writes:
> > a 14 drive stripe will max out the PCI bus long before anything else,
> Hopefully anyone with a 14 drive stripe is using some combination of 64 bit
> PCI-X cards running at 66Mhz...
> > the only reason for a stripe this size is to get a total accessible
> > size up.
> Well, many drives also cuts average latency. So even if you have no need for
> more bandwidth you still benefit from a lower average response time by adding
> more drives.
> -- 
> greg
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