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Unread 10-03-2002, 11:38 AM   #19
gmat
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Join Date: Mar 2001
Location: France
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Thats a point. But even ATA Raid is more costly in terms of system resources than single SCSI drive.
BB2K i still dont see why you want Raid0+1. You running a big web server ?
Yes as far as money goes SCSI units are *way* more expensive than ATA ones. But consider those gains:
- speed
- mechanical superiority (=greater reliability)
- speed
- lower system resources
- speed
- lower overall noise/heat (compared to ATA Raid...)
- did i mention speed ?

If i had to choose between a RAID of 5400rpm barracuda's that have 1y warranty, and a single SCSI 15K drive with 3 to 5y of warranty, it would be the 15K drive. Why ?
Look the figures (storagereview.com). One 15K unit is *quiet* even compared to 7.2K ATA units. Heat problem ? No more heat problem with modern drives. You pay a premium price, but you got what you paid for - a mechanical jewel.
(side note: it seems that 15K drives are generally quieter than 10K ones...)

Ah about transfer rates. You must take the protocol into account. With SCSI the controller (usually a powerful RISC chip) manages the transfer and concurrent accesses. With IDE each drive try to get the bus for itself. That was a short explanation but there are several good documents about this on the web. Anyway the result is - multiple drives live happier on a SCSI bus than on an IDE bus.
Another point, if you're considering a single drive, the fastest drive today is the Seagate Cheetah 15.3 which can transfer between 51 MB/s and 76 MB/s. The fastest IDE drive is the WD Caviar 800JB which does 29 MB/s to 49 MB/s... (figures range from inner platter zone to outer zone). And in no way two caviars in Raid0+1 will perform like a 15K.3, due to Raid overhead (and ATA-specific issues on top of this...)

In short, if money doesnt matter go SCSI. If you're on a budget, you're looking at the wrong site to begin with In any case, you always get what you paid for.

(edit) argh i forgot to mention access times. 15K drive access times contribute a *lot* to the 'snappiness' of operations... Why did ppl like old Quantum drives, because those old drives had the lowest access times around...
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