-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 A couple of very interesting studies have come out recently about the reliability of hardware, specifically disks:
This site summarizes it nicely: http://storagemojo.com/?p=378 With Google's actual paper here here: http://labs.google.com/papers/disk_failures.pdf But perhaps more interesting is this one: http://www.usenix.org/events/fast07/tech/schroeder/schroeder_html/index.html also summarized here: http://storagemojo.com/?p=383 I have read the entirety of both of the papers. Executive summary of these two papers: - - MTBF is useless - - SCSI, FC, SATA, ATA are equally reliable (surprising and embarrassing to people who have spent big bucks on SCSI/FC but both studies came to the same conclusion based on 100,000 disks each) - - Reliability between "enterprise" and "consumer" drives is the same - - Temp up to 40C doesn't make much difference in reliability (surprising!) - - SMART is semi-useful for predicting failures but only catches half of failures - - There seems to be no correlation between workload and failure rate - - The chances of a double failures in a RAID5 are much greater than we think. It seems mirroring remains a good idea. I didn't quite understand all of the reasoning in the second paper about long term auto-correlation and decreasing hazard rates. They seem to say that statistically speaking one disk failure now suggests greater chance of another disk failure coming soon which bodes ill for RAID5. IIRC a fellow KPLUGger had a double-failure in a RAID5 this week. - - There is no infant mortality phase for drives nor is there a particular age at which they tend to die (no "bathtub curve" typical for consumer products). Rate of drive failure is initially low but steadily increases as they age. Unfortunately google wussed out and won't tell us whose drives are the most/least reliable. The second study didn't mention this either. I guess they are afraid of getting sued. - -- Tracy R Reed http://ultraviolet.org D4A8 4860 535C ABF8 BA97 25A6 F4F2 1829 9615 02AD Non-GPG signed mail gets read only if I can find it among the spam. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFF2+Fb9PIYKZYVAq0RAn5nAJ0Twtnny94kdIOuoMROYvsXPcUB4wCglujT e5xSMhCWl+S99pVJBiFTl7Q= =uZ+3 -----END PGP SIGNATURE----- -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
