[mythtv-users] 2 TB Hard Drive Recommendations
drescherjm at gmail.com
Tue Dec 7 22:31:17 UTC 2010
On Tue, Dec 7, 2010 at 5:22 PM, Robin Hill <myth at robinhill.me.uk> wrote:
> On Tue Dec 07, 2010 at 04:02:04PM -0500, John Drescher wrote:
>> > Note that Green drives are not recommended for raid arrays because of timing
>> > out and goofing your raid array. WD's "RE" (RAID Edition) HDDs support
>> > Time-Limited Error Recovery ("TLER" ):
>> > More info here:
>> > http://www.tomshardware.com/forum/251076-32-raid-issues-western-digital-hard-disk
>> > I went WD Black RE's and they are speedy and have been reliable.
>> TLER is not necessary on linux software raid or zfs raid. It is needed
>> on hardware raid or on windows software raid.
> No idea where you get that from. Linux software raid is certainly
> affected by read errors causing long lockups (which TLER dramatically
> reduces). I don't know about ZFS, but I really doubt that it isn't
> affected - working around it would be enormously complicated (you'd need
> to timeout the read request in the driver and fall back to parity, keep
> track of when the drive does actually starts responding again, then deal
> with rewriting the bad block, all the time preventing any other read
> requests to the drive and keeping track of pending writes).
> That's not to say that drives without TLER can't be used though - you
> just have to accept the array locking up for 10s of seconds occasionally.
The difference is on HW raid or windows software raid or fake raid the
drive will be kicked out of the array during a long delay when the
drive tries to fix a URE. On mdadm the drive will not be kicked out of
the array but it may like you said be offline for > 10 seconds.
More information about the mythtv-users