Re: RAID 5 and postgresql

Hi,

> 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.

Don't forget the battery backed cache for write performance. And because the
controller doesn't know about the RAID array booting can become a problem
when your first drive breaks.

> 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.

The Dell OpenManage tools can help you with that, and if the controller
fails (never happened yet here) you can just call Dell support, and within 4
hours they bring you a new one. (I had some strange problems with a server,
and Dell replaced the mainboard and memory very quickly)

I still choose the Dell LSI-based PERC4/Di where possible.
- Sander