[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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