Spares and partitioning huge disks

[maarten <maarten@ultratux.net>]

Hi

I just got my 4 new 250GB disks.  I have read someone on this list advocating 
that it is better to build arrays with smaller volumes, as that decreases the 
chance of failure, especially failures of two disks in a raid5 configuration. 

The idea behind it was that since a drive gets kicked when a read-error 
occurs, the chance is lower that a 40 GB part develops a read error than for 
the full size 250 GB.  Thus, if you have 24 40GB parts, there is no fatal two 
disk failure when part sda6 and part sdc4 develop a bad sector at the same 
time. On the other hand, if the (full-size) disk sda1 and sdc1 do fail at the 
same time, you're in deep shit. 
I thought it was real insightful, so I would like to try that now.

(Thanks to the original poster, I don't recall your name, sorry)

Now my two questions regarding this.

1) What is better, make 6 raid5 arrays consisting of all 40GB partitions and 
group them in a LVM set, or group them in a raid-0 set (if the latter is even 
possible that is) ?

2) Seen as the 'physical' volumes are now 40 GB, I could add an older 80GB 
disk partitioned in two 40GB halves, and use those two as hot-spares. 
However, for that to work you'd have to be able to add the spares to _all_ 
raid sets, not specific ones, if you understand what I mean.  So they would 
act as 'roaming' spares, and they would get used by the first array that 
needs a spare (when a failure occurs of course).  But... is this possible ? 

Thanks for any insights!
Maarten

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