Re: thin provisioned LUN support & file system allocation policy

jim owens
2008-11-07T16:07:54Z

We have become confused and combined 2 independent issues...

UNMAP thin storage array provisioning is not SSD TRIM.

AFAIK the SSD trim will be handled just fine by sending the
small size (merged when appropriate) trim command.

The UNMAP is a big JBOD array problem and the solution(s)
are different. As I said to one of Ric's early posts,
my opinion is

- expensive array vendors need to do this themselves
because their whole thin provisioning thing is all
about sharing on different host types with existing
filesystems that use small blocks.

- linux filesystems that can do large allocation blocks
would be able to be tuned at mkfs to the array geometry
if the vendors give us the data... and we should only
optimize those filesystems and forget about trying to
fix it in the block layer or fix it with some kind of
defrag/scanner.

jim