IDE RAID controllers

[Dan Strick]

On Wed, 1 Oct 2003, irvine at sanbi.ac.za wrote:
> Anyone used any IDE RAID controllers recently under FreeBSD?
> 
> I've found the Promise Fastrak stuff works really well for 0 & 1 but
> doesn't support RAID 5.
> 
> We need a big filesystem, doesn't need to be all that fast or reliable,
> and were ogling the new-ish 250GB Western Digital drives.
> 
> We've found a case that will accomodate 6 drives, cooled properly, and
> were wondering what chance there was of getting a bit over a terabyte with
> a system drive into a FreeBSD box?
> 
> ie, something like an 80GB boot drive and 5 x 250GB IDEs in RAID5, or even
> just striped.
> 
> Our beige box supplier is very good on the hardware front but doesn't know
> much about FreeBSD and has had trouble with the more fancy Promise
> controllers with RAID 5 under other OS's.

What are your priorities?  You wrote that the file system doesn't have to
be "all that ... reliable."  If that is the case, you don't need RAID 5.
(But are you prepared to frequently dump and restore a huge file system?
Somehow the pain seems to increase with file system size faster than O(N).)

You wrote that you have had good experiences with Promise RAID controllers.
Why not continue using a brand you feel comfortable with?  Is the issue
really RAID 5 even though you think you don't need the extra reliability?

Have you considered using vinum?  It comes standard on FreeBSD and supports
various RAID flavors, including RAID 5.  All you need is a disk controller
that supports a whole bunch of disk drives.

I can't actually recommend vinum because I have never used it.  I just
know it exists.  I wonder about vinum RAID 5 performance because RAID 5
works best with NVRAM and as far as I know the vinum man pages don't say
anything about NVRAM.  I also wonder about the cheap "RAID" controllers.
I don't think they have NVRAM and I think most of them don't claim to
suppport RAID 5 either.

The most capable RAID cards seem to be SCSI and cost a lot more than
the cheap ATA cards.

I recently went looking for PCI ATA cards in the FreeBSD HARDWARE.TXT
file.  The only brands I found were HighPoint, Promise and 3Ware.
(Most of the ATA controllers listed were actually cpu support chipsets.)
The ATA cards with more than 2 ports all seem to be RAID cards.
I have not yet used any of these cards.  I don't know anything about
their RAID drivers.

Something else to watch out for: really huge file systems require a lot
of main memory for support.  For example, fsck memory requirements
increase with file system size.  I don't think you will have a problem
at only 1000 GB, but I am not certain.  This issue was discussed recently
on one of the FreeBSD mailing lists.

Dan Strick
strick at covad.net