Yes, there are reliability differences between SCSI and ATA drives. There are some things that are done in SCSI drives to make them more reliable for a wider variety of environments. But the thing to keep in mind is that high speed SCSI drives HAVE to have more advanced engineering applied to deal with the high RPMs.
For instance, a 15,000RPM drive generates a heck of a lot more heat than a 7,200RPM drive and heat is the enemy of all electromechanical components. So, the SCSI drives have more reliability engineering applied. As ATA drives obtain higher speeds, they take advantage of the technologies that were developed and deployed and have been cost-reduced for SCSI drives. The reliability of new 10,000RPM SATA drives will be very interesting to observe and compare to SCSI when it crosses the 10,000 barrier.
So let's think practically for a minute. If you look at MTBF numbers, do you feel that you are at a far greater risk with ATA? The answer is probably no because statistically they have you covered for far longer than you need. Bearing failures are the main reason disk drives fail over time. If a disk drive fails after five years, does it matter to you? Has it already exhausted its useful life? Is there a reason to believe that a slower RPM ATA drive will have more bearing failures than a faster RPM SCSI drive?
The final point that needs to be made is this. If you use ATA or SATA drives with RAID for device redundancy, the slightly higher failure rate of ATA drives does not make a difference.
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This was first published in April 2003