Re: RAID 5 and postgresql

At 10:01 AM 1/23/2006 -0600, Scott Marlowe wrote:

>I'm not sure if it's Dell's BIOS on the mobos, or something with the LSI
>cards, but the performance was substandard.
>
>So if you're working somewhere that you simply have to use Dell (not
>uncommon), at least make sure you get the LSI based RAID controller.

How about software RAID?

Linux software RAID appears to perform better than most RAID controllers
except perhaps those that can do read interleaving for RAID1 (I believe
some 3ware controllers can do it). Linux RAID mirroring doesn't do read
interleaving, only read balancing, which may not be so good for a single
sequential read, but pretty good for concurrent sequential reads - each
drive in a mirror set can handle one sequential read.

I find many of these RAID controllers fail significantly more than basic
SCSI controllers (which hardly ever fail). And the support under Linux for
such controllers can be a bit patchy sometimes - you want to be able to
easily know if a drive has died.

It just seems strange to pay a fair bit for something that doesn't perform
well and is less reliable.

Of course you get the "convenience" of the RAID stuff being abstracted away
so it just looks like one drive.