ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks

[Patrick M. Hausen]

Hi, all,

Am 09.01.2011 um 11:03 schrieb Matthew Seaman:

> [*] All of this mathematics is pretty suspect, because if two drives
> fail simultaneously in a machine, the chances are the failures are not
> independent, but due to some external cause [eg. like the case fan
> breaking and the box toasting itself.]  In which case, the comparative
> chance of whatever it is affecting three or four drives at once renders
> the whole argument pointless.


I assume you are familiar with these papers?

http://queue.acm.org/detail.cfm?id=1317403
http://queue.acm.org/detail.cfm?id=1670144

Short version: as hard disk sizes increase to 2 TB and beyond while the URE rate
stays in the order of 1 to 10^14 blocks read, the probability of encountering an URE
during rebuild of a single parity RAID approaches 1.

Best regards,
Patrick
-- 
punkt.de GmbH * Kaiserallee 13a * 76133 Karlsruhe
Tel. 0721 9109 0 * Fax 0721 9109 100
info at punkt.de       http://www.punkt.de
Gf: Jürgen Egeling      AG Mannheim 108285