Hi Thorsten, I'd guess that the cache installed on each drive will also have an effect, as will the kind of data you're working with (I'm guessing you have a good reason for the 10Krpm drives), so I doubt any theoretical reply is going to match the "real" answer, which would only be obtained from testing various scenarios - do let us know how the tests turn out if you choose this path. BTW - I noticed recently (using IBM's excellent "DFT" - drive fitness test - disk, that identical looking drives with identical model numbers can have different sized RAM caches on them) - and of course that DFT tells you what the installed cache on each drive really is :-) Kind Regards, Chris Drake Monday, May 17, 2004, 10:01:27 PM, you wrote: TJ> 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? TJ> Read performance will be as fast as the 10000 rpm raid can read. Write TJ> performance will go down to the write performance of the 7200 rpm raid (or TJ> even slightly lower). TJ> But this is only a generall answer as it depends on the speed of the TJ> individual harddisks. The 7200 rpm disk with higher capacity _may_ be as TJ> fast as the 10K rpm disk with lower capacity because the 120GB disk can TJ> read more data per rotation (depending on the geometry of the disk). TJ> 10000 rpm is a 38% speed increase over 7200 rpm, 120 GB is a 67% capacity TJ> increase over 72 GB. A portion of these 67% will go to more tracks/disk, TJ> but TJ> it _may_ happen that the 120 GB disks are as fast as the 10K 72 GB disks. TJ> Maybe its worth playing around with the disks to get the ideal TJ> performance. TJ> Viele Grüsse, TJ> Thorsten
