[KLUG Members] Re: SuSe 9.1 Linux Software RAID

[Adam Tauno Williams]

> > > It turns out that the Promise Fasttrack doesn't work with the 2.6
> > > kernel. It looks like the ataraid no longer exists in the 2.6 kernel
> > > in SuSe for the time being.
> > Take a look at the details of how it's "not supported".  Hardware-wise
> > the Promise cards, and most others like them, are a standard IDE
> > controller and a bit of BIOS that lets you boot.  The RAID
> > calculations are done in a fancy driver.
> True.

Yep.  ATA RAID on a single bus is silly anyway since a failed device
easily kills the buss - so no point in that;  hopefully these cards
don't do that but provide a bus for each device.

Otherwise I've found MD (software RAID) to be bloody fast,  faster even
than some crappy SCSI RAID cards (Adaptec HostRAID, for instance, really
sucks).

> While doing some research on 2.6 and RAID, I found a thread with Alan
> Cox with the following points:
> 1. Many of those IDE RAID cards are entirely software driven. Like
>    WinModems, you're not getting the meat of RAID, mirroring and
>    striping -- you're just getting a controller with extra IDE busses.
> 
> 2. Most RAID cards use proprietary formats on the disks. Meaning, you'd
>    better ALWAYS have one spare controller to pull your data off in case
>    of probelms.

Yikes!

> If work is paying for this, obviously #2 isn't a problem. But if work is
> paying for it, get real RAID controllers, and get SCSI while you're at
> it. Otherwise, md is probably a cheaper, more portable deal.

That would be my suggestion if you really want BANG.

IBM ServeRAID SCSI RAID controllers can be found on E-Bay for excellent
prices.  I've purchased varieties of these for ~$30-40.

For instance there is currently a ServeRAID-3H for sale with a
buy-it-now of $40.00.  Thats a three channel Ultra2 adapter (80Mbps)
with on board cache (usually 32Mbps), a RISC processor, and support for
a battery backup to the RAID cache. 

And with 36Gb Ultra2 IBM drives selling at $40-50 you can get some real
storage and performance.