On 4/3/12 6:50 PM, Bob Friesenhahn wrote:
On Tue, 3 Apr 2012, Julian Elischer wrote:
for flash drives this is great news..
Now if ZFS would get trim support, that too would be great.
The major unknown issue with trim is how well the drives
schedules/defers the trim operation so that it does not interfer
with other I/Os. Also, it would be really bad if the drive applied
trim after the block had been re-allocated for a write. It would
also be really bad if the drive loses unrelated data if there is a
power fail during trim.
If writes get blocked by a pending trim, then trim would not help
very much.
well since I work for the "drive manufacturer" I can say that in
this case it really is worth it.
:-)
But I'm glad that it is getting out there that trim aint as easy as it
seems.
The hard part about trim is making it so that if you get a power
failure, the trimmed data says
trimmed.
In some cases, it is not important. For example when a filesystem is
used, trimmed data will
never be accessed again without first writing new data to that
address. but for any application that assumes that trimmed data will
return zero's it is a critical feature.
Bob
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