Re: autovacuum

On 9/20/07, Robert Fitzpatrick  wrote:
> On Thu, 2007-09-20 at 16:38 -0400, Bill Moran wrote:
> > In response to Robert Fitzpatrick :
> > Why does everyone leave of the IO subsystem?  It's almost as if many
> > people don't realize that disks exist ...
> >
> > With 2G of RAM, and a DB that's about 3G, then there's at least a G of
> > database data _not_ in memory at any time.  As a result, disk speed is
> > important, and _could_ be part of your problem.  You're not using RAID
> > 5 are you?
>
> Yes, using RAID 5, not good? RAID 5 with hot fix total of 4 drives. All
> SATA 80GB drives giving me little under 300GB to work with.

RAID5 optimizes for space, not performance or reliability.  It gets
faster but less reliable as it gets bigger.  If you can afford the
space RAID-10 is generally preferred.

Note however that it is far more important for most general purpose
servers to have a RAID controller that is both fast by nature (i.e.
not $50.00) and has battery backed cache with write thru turned on.

RAID5 on a fast controller with battery backed cache is ok.  But I've
seen software RAID-10 outrun it for certain loads...