thin provisioned LUN support

Ric Wheeler
2008-11-06T14:43:23Z

After talking to some vendors, one issue that came up is that the arrays
all have a different size that is used internally to track the SCSI
equivalent of TRIM commands (POKE/unmap).

What they would like is for us to coalesce these commands into aligned
multiples of these chunks. If not, the target device will most likely
ignore the bits at the beginning and end (and all small requests).

I have been thinking about whether or not we can (and should) do
anything more than our current best effort to send down large chunks
(note that the "chunk" size can range from reasonable sizes like 8KB or
so up to close to 1MB!).

One suggestion is that a modified defrag sweep could be used
periodically to update the device (a proposal I am not keen on).

Thoughts?

Ric