RAID 5 solutions?

Lou Kamenov lou.kamenov at
Tue Nov 26 13:25:50 GMT 2002

In some email I received from Paul Robinson <paul at> on
Tue, 26 Nov 2002 13:13:34 +0000 :
> On Nov 26, Lou Kamenov <lou.kamenov at> wrote:
> > Nope, IDE and SCSI drives structurally are the same, the bus
> > makes the difference. The IDE bus is built on AT bus interface, 
> > where the SCSI logic board uses extra SBIC chip.
> Which, it has to be said, makes a whole world of difference. In the
> past I've had various issues with SCSI, Fibre channel and IDE setups.
> They all have their advantages and the flips sides as well of course.
> > Comparing donkey with a van eh?
> > I`d use SCSI if the drive has to operate with loads of data hungry
> > tasks. And i mean *really hungry* multitasking, not a Samba/NFS
> > server with 10 users.
> We use SCSI when we want RAID - full stop. IDE RAID is fine, but it
> just seems clunkier. Oh, and of course we use SCSI for the tape
> systems.
> > Yes, a SCSI controller is able to control everything without any
> > work of the processor. However I disagree a bit with that. "A LOT"
> It's relative, and depends on the processor. If a processor is going
> to spend say 'X' thousand instructions a second dealing with the disk,
> as to whether that constitutes "A LOT" depends on how many
> instructions a second the processor can do total. 

However there is a new breed of processor out there, let say 
transmeta`s Crusoe and code morphing.. it is amazing..

> Sure, you might not
> notice much with a P4 2Ghz machine, but if all you have is an old
> 486SX and you're trying to run X at the same time...

Exactly, or AMD`s Athlon XP/MP series..

> > Basically all the drives on the SCSI massive are able to operate at
> > the same time, with IDE the things are a bit different, it`s limited
> > to a 2 drives in a massive which cant operate at the same time,
> > hence they must take turns.
> Which is one of the several reasons they are clunky, nasty and not
> suited to RAID, IMHO. Although you can build a few terabytes of
> storage for less than £5k these days, which is nice if you just want a
> backup server.

It really depends :) correct me if I`m wrong.
> > Right.
> > However we all know the MTBF of a SCSI. 
> > You`ve to ask yourself, do you really need SCSI?!
> I've never had a SCSI disk fail on me. Seriously. Perhaps I'm out on
> the 95th percentile to the 'M' in MTBF. ;-)
Come on, we all know how many fans you need to keep a SCSI working :)

> Just going back to the terabyte stuff above, some of you who are
> looking at large RAID solutions might want to take a look at the
> NAS/SAN/Direct-attatched stuff under the "Teravault" name that they're
> doing at - it looks decent kit and the pricing isn't bad
> (3.2TB for less than £10k + VAT). I've had server kit off them in the
> past (including the one I'm writing this on)  and it's high-quality
> stuff.

And what do you have at the end? 
Super-duper server and one point failure?
Anyways, that`s offtopic.



Lou Kamenov	lou at		lou at
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