RAID5 for Linux

[dave at microway.com (David Backeberg)]

Bob:

You've already seen everybody else's answers about how many disks you can use. 
A card I haven't seen mentioned is the 3ware line of raid cards. There's an 
8-port SATA card from 3ware called the 8506-8 I've played with using linux 
software raid. You can have it export all the drives as JBOD and I've found 
that linux software raid5 running on a dual proc xeon box can run the drives 
about twice as fast as the controller chipset running raid5 on the card. 
(115% quicker with some quick hdparm checks)

BTW, what makes you want SATA? I've never seen anybody do true "hot swap" with 
SATA drives, but that doesn't mean it's impossible. The swapping I've seen 
is:
1) turn off the system
2) pull out the quick-release drive from its bay
3) put a different drive into the bay
4) turn the system back on

Which is nicer than opening a chassis and moving cables around, but it's not 
true hot swap. Has anybody actually hot-plugged a SATA drive under linux? If 
the scsi bus can handle it, then this should be possible, since at least with 
the 3ware card with JBOD, the disks show up as scsi devices.

And how much money are you planning to spend? If you want to rack mount this, 
there are several chassis that have integrated hot-swappable backplanes.

And what are you using for cpus/ram, etc? If you're going software raid, its 
your cpu(s) that are doing the work of running the raid...

On Tuesday 27 April 2004 17:06, Bob Keyes wrote:
> At my new job, we have a NAS "Snap Appliance", which is pretty horrible
> and I want to get rid of it. So I am going to push for a Linux solution.
> I'd want RAID level 5, and Serial ATA drives, and of course linux
> niceness. I was looking at the Adaptec 2810SA, but it's got 8 ports..I
> though you needed 9 for RAID5 (one for each bit plus one parity) or am I
> misunderstanding this? I'd also want hot-swappable. Anyone have any
> suggestions?
>
> For backup, I am thinking the Sony AIT-2 changer, LIB-D81/A2. Don't know
> if it's compatible with Bacula though...
> _______________________________________________
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-- 
David Backeberg (dave at microway.com)
Microway Technical Support - http://www.microway.com

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