Subject: Re: using different RAID types on the same disk array
To: Geert Hendrickx <ghen@NetBSD.org>
From: Greg Oster <oster@cs.usask.ca>
List: netbsd-users
Date: 12/20/2006 13:35:30
Geert Hendrickx writes:
> Hi,
> 
> looking for some advice on RAIDframe here;
> 
> On a machine with two SATA disks, is it a good idea to create
> RAID-1 (mirror) and RAID-0 (stripe) arrays on the same set of
> disks?  I'd like to have the benefits of RAID-1 for my system
> and data partitions and RAID-0 for all recoverable data like
> /tmp, cvs trees, obj and work dirs, ...

I'd put /tmp on RAID-1 too :) 

> How will the interference between the two raid arrays impact
> performance?  For example when reading from both parts at the
> same time, will the RAID-1 automatically read from a disk not
> being accessed by the RAID-0, or not?

RAIDframe won't make that distinction...  But if you're reading 
any sort of big files from the RAID-0 you're going to be using both 
disks anyway, and it won't matter which disk the RAID-1 picks for 
a particular IO.
 
> Or should I use the drives independantly?

My gut reaction is that with RAID-1 and RAID-0 you won't notice any 
performance issues in day-to-day use...  So just pick the setup 
appropriate for safeguarding your data and run with that...

Later...

Greg Oster