I overlooked that when I posted this message; I totally forgot about the
write penalty. Sorry about that.
-----Original Message-----
From: John White [mailto:[EMAIL PROTECTED]]
Sent: Friday, July 14, 2000 7:08 PM
To: qmail mailing list
Subject: Re: questions about performance and setup
On Fri, Jul 14, 2000 at 12:21:57PM -0700, Jason Murphy wrote:
> The machine I built contains a DPT SmartRAID V SCSI RAID 0/1/5
controller
> with 5 10000RPM 9.1 gig drives. The thing I notice about RAID 5 in the
> right configuration is that you can throw tons of IO at it and you will
> see little decrease in performance. Our Database server (Ya, I know, its
> not MAIL SERVER) gets tons of IO and its nothing to it; just eats it up
> and continues on its way.
A massive mail injection, especially if the content is unique to the
user, can overwhelm a disk subsystem.
This is reccomending the exact -wrong- kind of disk system. RAID 5
has a write penalty, as it has to calculate parity for each write,
and write to multiple spindles.
The best type of RAID for small block writes is RAID 10 or RAID 1+0
(not to be confused with RAID 0+1). Even better is to use a disk
system with write-back cache. Ideally, you need at least seven
spindles.
I've seen great things with the Infortrend controller.
A great setup would be 1U pc's connected to an external RAID.
John
smime.p7s
