On Mon, Nov 21, 2005 at 10:34:36AM +0100, Mario Splivalo wrote:
> > RAID5 generally doesn't make for a fast database. The problem is that
> > there is a huge amount of overhead everytime you go to write something
> > out to a RAID5 array. With careful tuning of the background writer you
> > might be able to avoid some of that penalty, though your read
> > performance will likely still be affected by the write overhead.
>
> RAID5 was not ment to improve performance, but to minimize disaster and
> downtime when your hard disk dies. We're using RAID5 with postgres. In
> the last 3 years we changed 5 disks, but the system downtime was zero
> minutes.
And the same would have been true with RAID10. In fact, RAID10 is more
reliable than RAID5; depending on what drives fail it's possible to lose
up to half of a RAID10 array without any data loss. If you ever lose
more than 2 drives at once with RAID5, your data is gone.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461