On Tue, 28 Apr 2009, Miles Nordin wrote:
* it'd be harmful to do this on SSD's. it might also be a really
good idea to do it on SSD's. who knows yet.
SSDs can be based on many types of technologies, and not just those
that wear out.
* it may be wasteful to do read/rewrite on an ordinary magnetic
drive because if you just do a read, the drive should notice a
decaying block and rewrite it without being told specifically,
maybe. though from netapp's paper, they say they disable many of
Does the drive have the capability to detect when a sector is written
to the wrong track? In order for it to detect that, the expected
location would have to be written into the sector.
In the end, though, I bet we may end up with this feature on ZFS in
the disguise of a ``defragmenter''. If the defragmenter will promise
to rewrite every block to a new spot, not jhust the ones it pleases,
this will do the job of your ``write scrub'' and also solve the drive
caching problem.
It seems doubtful that bulk re-writing of data will improve data
integrity. Writing is dangerous.
Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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