RAID 0+1 using 10000rpm and 7200rpm HDD?

[Thorsten Jungblut]

Hi

> RAID 0 (on Intel IHC5-R)
> Western Digital Raptor 74GB 10000rpm SATA
> Western Digital Raptor 74GB 10000rpm SATA
> 
> RAID 0 (on Promise FastTrak 378)
> Seagate Barracuda 7200.7 120GB 7200rpm SATA
> Seagate Barracuda 7200.7 120GB 7200rpm SATA
> 
> I would like to create a RAID 0+1 from this config but I wonder if I'm
> about to loose on performances doing the RAID 1 between the two (2) RAID 0
> volumes since the first volume has 10000rpm HDD and the second one has
> 7200rpm HDD.
> 
> What do you think?

Read performance will be as fast as the 10000 rpm raid can read. Write 
performance will go down to the write performance of the 7200 rpm raid (or 
even slightly lower).
But this is only a generall answer as it depends on the speed of the 
individual harddisks. The 7200 rpm disk with higher capacity _may_ be as 
fast as the 10K rpm disk with lower capacity because the 120GB disk can
read more data per rotation (depending on the geometry of the disk).
10000 rpm is a 38% speed increase over 7200 rpm, 120 GB is a 67% capacity 
increase over 72 GB. A portion of these 67% will go to more tracks/disk, 
but
it _may_ happen that the 120 GB disks are as fast as the 10K 72 GB disks.

Maybe its worth playing around with the disks to get the ideal 
performance.

Viele Grüsse,
Thorsten

-- 
Thorsten Jungblut
Universität Koblenz, Fachbereich Informatik
 http://www.netcorner.org/