atacontrol raid1 vs. gmirror

[Paul Mather]

On Sat, 2005-06-11 at 14:42 -0400, Mike Jakubik wrote:
> Can someone explain tome the difference between a RAID1 setup done via
> atacontrol and gmirror? I have a VIA 6420 SATA150 controller, which also
> has raid, but is not supported by -stable.

Here are the main differences, as I see them:

atacontrol RAID:

- Only for ATA;
- Compatible with quite a few ATA RAID card BIOS metadata formats, hence
you can create the RAID using the RAID controller's BIOS menu;
- Supports only two-way mirroring (IIRC);
- Supports spares.

gmirror:

- Works with any GEOM provider (ATA, SCSI, ggate, etc.);
- Uses the last sector of each RAID component to store its own metadata;
- Supports N-way mirroring;
- Does not support spares (though gmirror activate/deactivate can be
used to associate a component with a mirror somewhat akin to having a
spare).


I found array rebuilding to be troublesome on atacontrol RAID---so much
so I abandoned it and used vinum and then gmirror instead for my RAID 1.
(I have a bootable geom_mirror setup, now.)  Mind you, that was in the
pre-ATA mk.III days, and I hear the RAID support underwent a big revamp
in the mk.III rewrite.

Cheers,

Paul.
-- 
e-mail: paul at gromit.dlib.vt.edu

"Without music to decorate it, time is just a bunch of boring production
 deadlines or dates by which bills must be paid."
        --- Frank Vincent Zappa