Re: [gentoo-server] RAID

[Patrick Lauer]

On Wed, 2006-02-01 at 15:19 +0100, Ramon van Alteren wrote:
> >I'm running a software raid spanned over 3 controllers ... I'm not aware
> >of a hardware-based solution that even comes close to that flexibility.
> How many disks can you put in ?
> AFAIK most motherboard interfaces support 4 SATA disks
plop in another controller and it's +4 or more :-)
The onboard controllers are often cheap (SiL SATA) or broken (VIA
KT133), so usually you'll use a "known-good" PCI/PCIe controller to
avoid problems.

Right now the case (miditower) is limiting, but if I wanted I could get
a Promise TX4 for ~60Eur and add 4 SATA disks. 

The really cool thing with software raid is that you can just stuff any
block device in and it'll work - mix SCSI, IDE, SATA, md - you can stack
raid1 over raid0 if you want.
Just label all disks so that you know which one just died ...
 
> >But if you need a disk array with maximum performance I'd still suggest
> >a hardware-based solution.
> Me too :-)
> But considering your comments, why ?

Looking at benchmarks I can see ~500M/s from good controllers - it'll be
hard to get the same level without dedicating a whole CPU to that. SAN
boxen have wonderful managment features and belong into the "just
work(tm)" category - each linux software raid will have to be
consciously put together.

A 4U box which plugs in to a SCSI or FC port costs ~5k Eur, the same as
Do-it-yourself costs ~1,5k, but you don't get a fully tested solution
that really works. You'll have to see what happens if you yank out a
disk or two, you'll have to configure monitoring, etc. etc.

Now if you are a company you'll pay a small premium just so that you
don't have to care about any technical details ... time is money :-)
-- 
Stand still, and let the rest of the universe move