Such findings might spur some customers to, for example, buy more SATA drives to provide more backup or more parity drives in a RAID configuration to get the same level of data protection for a lower price. However, Garrett cautioned, SATA continues to be best suited for applications such as backup and archiving of fixed content (such as e-mail or medical imaging) that must be stored for long periods of time but accessed quickly when it is needed. FC will remain the "gold standard" for online applications such as transaction processing, he predicts.

Don't sweat the heat?

The Google study examined replacement rates of more than 100,000 serial and parallel ATA drives deployed in Google's own data centers. Similar to the CMU methodology, a drive was considered to have failed if it was replaced as part of a repair procedure (rather than as being upgraded to a larger drive).

Perhaps the most surprising finding was no strong correlation between higher operating temperatures and higher failure rates. "That doesn't mean there isn't one," said Luiz Barroso, an engineer at Google and co-author of the paper, but it does suggest "that temperature is only one of many factors affecting the disk lifetime."

Garrett said that rapid changes in temperature -- such as when a malfunctioning air conditioner is fixed after a hot weekend and rapidly cools the data center -- can also cause drive failures.