[mythtv-users] warning for anyone with western digital green drives
Michael T. Dean
mtdean at thirdcontact.com
Thu Jan 5 19:57:48 UTC 2012
On 01/05/2012 11:54 AM, John Drescher wrote:
> On Thu, Jan 5, 2012 at 11:47 AM, Ronald Frazier wrote:
>> Recently I got to poking around at the SMART data for all of my
>> drives. When I did, I noticed that one of my media drives...a 2TB
>> western digital green drive...had an interesting looking number for
>> one of it's parameters. The parameter was "Load Cycle Count" and the
>> value was over 500,000. I looked into it, and this value represents
>> the number of times the heads have been unloaded on the drive.
>> Apparently, in an effort to conserve power, the green drives are
>> exceptionally aggressive at this, unloading the heads after just 8
>> seconds of idle time. Over the 1.5 years I had this drive, that count
>> had reached over 500k. The alarming thing is that these drives are
>> only rated to handle 300k load cycles.
The design is validated to a million cycles, and WD expects them to
handle significantly more than that without issue. The SMART tools
report an incorrect maximum for the drives (they say 300K, but I don't
know whether that's because WD put the wrong value in or because the
tools are interpreting it wrong--i.e. as with Seagate, perhaps WD is
using a "proprietary" encoding for some values).
See http://wdc.custhelp.com/app/answers/detail/a_id/5357
-----
Some utilities, operating systems, and applications, such as some
implementations of Linux, for example, are not optimized for low power
storage devices and can cause our drives to wake up at a higher rate
than normal. This can negatively impact some of the power savings
associated with WD Green Power drives and artificially increases the
number of load-unload cycles. The increase in load/unload cycles for a
typical desktop user are within design margins (drive has been validated
to 1 million load/unload cycles without issue).
-----
However, 99.999992% of pages on the Internet just build off the hysteria
caused when someone noticed values in their SMART tool and thought, "I
suppose these hard drive engineers can't do math." (In other words,
it's hard to find any real information with all the panicked posts on
the 'net. :)
Note, also, the best fix for the issue is to fix your system to not
abuse the file system--i.e. configure your system to use it
appropriately. After all, if you actually let the drive idle, rather
than waking it every 10-30s, it will spend a majority of its time at
idle 3 power usage (0.7W) versus 3.3W at idle and 5.3W for read/write.
(Numbers based of WD20EARS -
http://www.wdc.com/en/products/products.aspx?id=120 ).
>> Apparently this is a very common problem noted by many linux users
>> with these drives. The way to solve this problem is download the
>> wdidle3 utility (you must boot into DOS to run it) and use it to
>> either disable the feature or set the timeout to a larger value.
>>
> I have a few of these drives (along with hitachi and samsung 2TB
> drives). I believe I set my idle time (with wdidle3) on these to
> whatever was the maximum 3hours? 6 hours?
On some drives, the max is 30s, on others, it's 300s (5m). On these
Green drives, it defaults to 8s. Note, also, that the wdidle3 tool is
not validated to run on any drives other than those listed at
http://support.wdc.com/product/download.asp?groupid=609&sid=113:
-----
This firmware modifies the behavior of the drive to wait longer before
positioning the heads in their park position and turning off unnecessary
electronics. This utility is designed to upgrade the firmware of the
following hard drives: WD1000FYPS-01ZKB0, WD7500AYPS-01ZKB0,
WD7501AYPS-01ZKB0.
CAUTION: Do not attempt to run this software on any hard drives other
than what is listed above. Please make sure that the computer system is
not turned off during the firmware upgrade. Doing so may damage the hard
drive beyond repair and your data may be lost.
-----
So, it's quite possible that changing the idle 3 timeout will invalidate
your warranty.
That said, it /is/ important that anyone with a WD Green configure their
system to use the file system properly. Again, see
http://wdc.custhelp.com/app/answers/detail/a_id/5357 for some
suggestions, but there are a lot more out there when you search on "low
power linux" or "laptop mode linux" or similar. Oh, and note, also,
that having only MythTV recordings on the drive may "solve" the issue
for you, too (assuming MythTV recording file writes are <8s apart, and,
IME, they seem to be).
Mike
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