Spin down HDD after disk sync or before power off
olli at lurza.secnetix.de
Wed Jan 27 12:35:15 UTC 2010
Alexander Best <alexbestms at wwu.de> wrote:
> because of kern/140752 i looked through a discussion back in 2009
> concerning freebsd's hdd spin down procedure. right now ATA_FLUSHCACHE is
> being used although the hitachi hdd specs referenced in the pr say that this
> will not cause proper load/unload and thus an emergency unload will occur
> which reduces the life expectancy of hdds dramatically (20.000 shutdowns vs.
> 600.000 shutdowns). unfortunately the discussion back then didn't come up with
> any sort of decision/patch.
> attached you'll find a very simple patch which issues ATA_STANDBY_IMMEDIATE
> instead of ATA_FLUSHCACHE during hdd spin down.
A few comments ...
First, you should not *replace* ATA_FLUSHCACHE. Rather, you
should issue *both* commands, first ATA_FLUSHCACHE and then
ATA_STANDBY_IMMEDIATE (maybe with a short delay between, just
to be on the safe side).
Second, you should make sure that ATA_STANDBY_IMMEDIATE is
only used when a poweroff is requested, but not in other
cases. Of course, ATA_FLUSHCACHE should *always* be sent.
Finally, it would be nice if it is put under a sysctl or
similar, so the feature can be switched on and off.
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