[Nottingham] Big biiig problem regarding IDE-RAID

[Robert Davies]

On Tuesday 15 Jul 2003 13:26, Graeme Fowler wrote:

> On Tue, 15 Jul 2003, Martin wrote:
> > IDE-RAID is all well and good if supported. Unfortunately, some of the
> > later Promise chipsets are not useable yet via Linux. Also depends on
> > how good the BIOS support is also...
>
> I've spent a proportion of the morning running a new Intel server mobo with
> integrated IDE-RAID through its' paces. First observation was how slow it
> was to create the array as compared to (say) a Megaraid SCSI card (but then
> Adaptec cards take an unnecessarily long time, also).

That's odd, with software RAID 1, you can build it incomplete, then Hot Add 
the mirror after you've got the data installed, works quickly in background 
and isn't very noticeable to users of the system.

> First OS to attempt to install: RH9. It immediately saw both disks as
> separate devices (hde and hdg) instead of an array. So we toddle over to
> Promise's site and find the drivers for the Fastrak100 card (which the
> embedded chipset emulates, apparently) and find that they're identical to
> the ones on the Intel driver disk. And only go as far as RH7.3.
>
> Googling around we eventually found a thread which had hundreds of "IDE
> RAID, Promise card, install fails" entries... followed by a single "try the
> Fastrak 2000TX driver" entry. Boom! That driver not only supports all the
> cards, it goes through RH8 and 9 (as well as some slightly more esoteric
> OSes).

There's been a number of problems, and the Promise is covered by 2 sets of 
drivers, there was a bit of a fuss a while back over NDA's, Andre Hedrik fell 
out with Promise for a while, but i think they made friends again and got it 
sorted.

> Indeed. Also add the sub-category "those who are fed up paying through the
> nose for large capacity SCSI disks when IDE drives are now fast enough and
> vastly more capacious, at the same time as being a whole heap cheaper" :)

There's a number of issues though :

1)  IDE rated as 'consumer', lowering of warranties and attempts to claim the 
drives are not designed for 24/7 use.

2)  IDE drives lying about their caches, to do well on benchmarks.  This has 
made the write barrier stuff needed for journalling file systems in 2.4, much 
more complicated than it ought to be.

That said, I like some IDE RAID systems, and with serial ATA use of IDE drive 
connect, for RAID boxes with SCSI interfaces is going to be more and more 
common.  The IDE disks are so much cheaper and often higher capacity, you can 
simply go to RAID 10 and still save money over a SCSI RAID-5 setup, with 
better performance.

Rob