Hard Drives Made for RAID Use

An anonymous reader writes "Hard drive giant Western Digital recently released a very interesting product, hard drives designed to work in a RAID. The Caviar RE SATA 320 GB is an enterprise level drive without native command queueing and uses an SATA interface. In works better in RAID than other drives because of features like its time-limited error recovery and 32-bit CRC error checking, so it is an option when previously only SCSI drives would be considered."

Comments

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[cperciva]

On the newegg link they list the MTBF as 1 million hours. Google tells me that that is about 114 years. How can it have such high mtbf?

MTBF is defined as [short time period] * [number of drives tested] / [number of drives which failed within that time period]. An MTBF of 114 years doesn't mean that half of the drives will survive for 114 years without a failure; it means that if you run 114 drives for a year, you should expect to have 1 failure.

A more intuitive way of conveying the same information is to say that the drives have an expected failure rate of no more than 1E-6 per hour.

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[Rasta Prefect]

On the newegg link they list the MTBF as 1 million hours. Google tells me that that is about 114 years. How can it have such high mtbf? Is that newegg just not having correct data or is there something special about these drives (or are they designed to be "used" less)?

Easy: You, like most people, don't know what MTBF means. MTBF is only meaningful in context with the expected lifespan of the device. This is probably somewhere in the neighborhood of 5 years, or about 43,800 hours. Essentially, what the manufacturer is saying is "Based on some data, we estimate that if you run x number of these drives, the average time between failures will be 1,000,000/x hours, up until the expected lifespan of the drive, at which point all bets are off"

For computer hardware this is always some sort of extrapolated estimate, since they have of course not actually been testing the drive for it's expected lifespan, or it would be obsolete by the time they released it.