[Discuss] Adventures in N40L Land

[mark at buttery.org (Shirley Márquez Dúlcey)]

On 2/14/2012 10:59 AM, Jerry Feldman wrote:

> One issue with RAID is that you don't want to mix geometries. I like to
> keep 2 different makes of drives in my RAID because of different MTBFs.
> We've had simultaneous drive failure in the BLU servers, With 2
> different makes (or at least 2 different lot numbers) the chances of
> simultaneous disk failure is lower.

Small differences in geometry (slightly different numbers of blocks) 
aren't a problem; you just create the partitions to match the smallest 
drive. If the leftover space is large enough you can use it for a 
variety of purposes, including a boot partition (even a RAID 1 pair of 
them if you have a couple of matching spaces) or swap. Setting up boot 
from a RAID 5 is a pain if your distro supports it at all, so a vanilla 
boot partition is handy. Small amounts of leftover space get wasted, but 
what's a stray GB among friends?

Large differences and/or differences in block size are best avoided, 
though after the first 200GB drive failure it was replaced with a 250GB 
drive because 200GB drives were no longer readily available.

I ran a RAID 5 server with five 200GB drives for a few years; it was a 
media server for storing my music and video collection. There were three 
different brands of drives, and no two drives were from the same 
manufacturing lot as I had bought them one at a time whenever special 
deals were offered. I suffered two drive failures over that period, but 
they were widely separated and no data was ever lost.

After the second failure I replaced that with a RAID 1 pair of 1.5TB 
drives, and reused the four good drives in other servers (two servers 
with RAID 1 pairs in two email servers, one at my house and one at a 
friend's house). All are currently going strong.