On 05/11/2009 10:50 AM, Theodore Tso wrote:
On Mon, May 11, 2009 at 10:29:51AM -0400, Ric Wheeler wrote:
The key is not at the FS layer - this is an issue for people who RAID
these beasts together and want to actually check that the bits are what
they should be (say doing a checksum validity check for a stripe).
Good point, yes I can see why they need that. In that case, the
storage device can't just silently truncate a TRIM request; it would
have to expose to the OS its alignment requirements. The risk though
is that more they try push this compleixity into the OS, the higher
the risk that the OS will simply decide not to take advantage of the
functionality. Of course, there is the question why anyone would want
to build a software-raid device on top of a thin-provisioned hardware
storage unit. :-)
- Ted
Probably not as uncommon as you would think, but not as you suggest to raid thin
provisioned luns (those are done usually as RAID devices inside an array).
Think more of the array providing a thinly provisioned LUN made up out of T13
TRIM enabled SSD's devices internally. RAID makes sense here (data protection
is still needed to avoid a single point of failure) and the relative expense of
the SSD's devices makes "thin provisioning" really attractive to external users :-)
ric
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