[mythtv-users] warning for anyone with western digital green drives
PJR
pjrobinson at metronet.co.uk
Sun Jan 8 00:05:43 UTC 2012
The reason I said the discs were 'faulty' was because on running
smartctrl on both discs it terminated with an error, it reported Read
Failures consistently for the same LBA_of_first_error _not_ because of
the Load_Cycle_count value (I mentioned this in my first post to this
thread and the reason the discs have been returned to the supplier). I
was just reporting my Load_Cycle_count_values since this seemed to be a
direction the thread was going and the info might be useful.
On 07/01/12 17:28, Simon Hobson wrote:
> PJR wrote:
>> My two WDC WD10EARX-00N0YB0 (possibly faulty) drives have:
>>
>> 9 Power_on_Hours 190
>> 193 Load_Cycle_Count 1064
>>
>> 9 Power_on_Hours 175
>> 193 Load_Cycle_Count 1064
>>
>> I assume, if they weren't faulty this is not good?
> Why faulty ?
> The whole essence of this thread is that these drives have (by
> default) very aggressive power saving. If idle for just 8 seconds
> they will unload the heads - which I assume means moving them to a
> safe zone on the disk and lifting them. After this, I suspect there's
> another fairly short timer before they also spin down the drive.
>
> On a typical Unix [like] system, there are frequent disk accesses -
> checking this, logging that, etc, etc. So what tends to happen is the
> drive goes idle, unloads the heads, the system accesses it so it
> loads the heads, rinse and repeat often. So the Load_Cycle_Count
> which counts these will increment quite rapidly.
>
> The suggestion is that it better to increase the timeout, so under
> normal use they won't unload the heads very often, if at all.
> Say you accessed the drive every 30 seconds. On each access, the
> drive would load the heads, do the access, then 8 seconds later
> unload the heads again. So that's 120 load cycles per hours, or 2880
> load cycles per day !
> Increase the timeout to a minute or two, and under the same scenario
> you'd probably have none.
>
>
> Which reminds me I need to twiddle with some drives I use for
> backups. I bought a SATA card for the old Mac I use to run
> Retrospect, but kept getting some rather oddball errors, kernel
> panics, and so on. I thought the card might be faulty, but then
> twigged ...
> I've done a cron job which every minute updates a file on any of the
> backup disks that are mounted - which prevents the drive going to
> sleep and spinning down. I suspect the load cycle count will be going
> up quite nicely on them - up to 1440 per day while the drive isn't
> actually being accessed by the backup software.
> What was happening was that the backup software accesses the drive to
> see what it is, then goes off to find a client - it then scans the
> client, does a bit of thinking to decide what files need copying, and
> then starts copying files by which time the drive has got bored and
> spun down resulting in an error and/or kernel panic.
>
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