You may well be right for this class of machine. EIDE drives are 7200rpm and you'll get an average access speed of 9ms (or thereabouts). You'll get a sustained throughput of about 50Mb/s on the disks and whatever the array will support when you can double up on disks. With a SCSI array and 10K rpm disks you'll get an average access time of 6ms, with 15K disks you're down to around 4.5ms (I think those numbers are right. On the other hand, as you rightly point out, you can double the number of I/Os per second, for, oh, only two or three times the price :-) You can claw that difference back by having more EIDE drives (I don't know what the 3Ware controller supports).
I am less concerned with initial seek times than with overall throughput, although of course it's a parameter that needs to be considered. I do believe, however, that two things are true:
1. the multiple EIDE drives will offer performance that, while lower than equivalent number of SCSI disks, present a price/performance equation in most cases more attractive
2. one can match the RAID-5 performance of N SCSI drives with M EIDE drives, where M > N, and where total cost of the M solution still going to be significantly less than the N solution.
Of course, this may break down in higher-end scenarios, but for small and medium business I think it's valid.
And again -- if this is a production server you *must* consider support and maintenance. If you can't buy a supported machine with a 3Ware controller, pay the extra and get a SCSI machine which is supported.
And don't forget that the Megaraid controller and SCSI disks are well-established technology. There's a lot to be said for conventional technology when you're building a server -- servers really do need to be reliable.
3Ware has been around for quite a long time and has excellent support... I would definitely already consider them "conventional" technology. As for SCSI vs. EIDE vs. SATA, I'm sure they all work and don't by themselves affect MTBF in any meaningful way.
-- Rodolfo J. Paiz rpaiz@xxxxxxxxxxxxxx
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