Re: RAID - raidframe vs hardware/controller

[Matthias Scheler <tron%zhadum.org.uk@localhost>]

On Mon, Apr 18, 2011 at 06:59:51AM -0700, Paul Goyette wrote:
> I'm about to implement RAID in my home server, and would like to
> know the relative merits of using software raid(4) raidframe vs
> "hardware" raid as implemented in the hard-drive controller.

What RAID level do you want to use? RAID 5 in software isn't particular
fast (not really NetBSD specific). For RAID 1 hardware RAID controllers
don't provide performance benefits.

For NetBSD older than 5.1 you will also have annoying RAID rebuilds
after an ungraceful shutdown. This was however fortunately fixed in
NetBSD 5.1. On my server this reduce the rebuild of a 1.8TB RAID 1
from several hours to a few minutes. Hardware RAID controller
shouldn't require long rebuilds. They usually don't even require
rebuilds after crash, only after a power loss.

> Is it possible to use raid-set as boot device?

You can boot of RAIDframe RAID 1 devices as well as of hardware
RAID controlles if the later has a suitable BIOS.

> Are they equally confusing to configure (specifically WRT labelling!)?

With software RAID you usually create a RAID containing the full
physical disks (which requires labelling them) and later divide
the RAID volumes into partitions.

With an hardware RAID you usually create the RAID volumes before even
attempting to install NetBSD. Afterwards you deal with the RAID volumes
as if they were physical disks.

> Are they equally easy to "manage" (swap and rebuild failing member)?

NetBSD only supports RAID management for a few hardware RAID controllers.
The Intel RAID Controller SRCS14L which I used with NetBSD in the past
didn't and I had to to boot its management software of disks to
manage the RAID.

RAIDframe on the other hand allows full management from within NetBSD
which works very well.

        Kind regards

-- 
Matthias Scheler                                  http://zhadum.org.uk/