Dear Mikael Abrahamsson, In message <alpine.DEB.2.00.1301190838440.12098@xxxxxxxxxxxxxxxx> you wrote: > > > If my math is correct, with a URE rate of 10E14, that's one URE for > > every ~12.5TB read. So theoretically one would have to read the entire > > 2TB drive more than 6 times before hitting the first URE. So it seems > > unlikely that one would hit a URE during a mirror rebuild with such a > > 2TB drive. > > Unlikely yes, but it also means one in 6 rebuilds (statistically) will > fail with URE. I'm not willing to take that chance, thus I use RAID6. Me too, as actually it will be probably more than one out of six failing. The URE rate as published in the drive's documentation is only true under specific conditions. These conditions may not be met during extended periods of more or less continuous operation of the drive, like during backups or RAID array rebuilds. For example, years ago we had repeated cases of double errors taking down RAID 5 arrays with Maxtor MaXLine Plus II 7Y250M0; the pattern was always the same: a disk error during a backup run, followed by another disk error during rebuild. This specific drive type gets extremely hot under continuous operaton, which greatly shifts the URE rate to the worse. So even if the failure rate appears to be acceptable in theory, it may bite you hard when you lose your data in reality. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@xxxxxxx Alliance: In international politics, the union of two thieves who have their hands so deeply inserted in each other's pocket that they cannot separately plunder a third. - Ambrose Bierce -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
