XFS support for TRIM / blkdev_issue_discard?

[Martin K. Petersen]

>>>>> "Peter" == Peter Niemayer <niemayer at isg.de> writes:

Peter> And I did not find any requirement or hint to "tell the largest
Peter> free space around the area just freed" in
Peter> http://www.t13.org/Documents/UploadedDocuments/docs2008/e07154r6-Data_Set_Management_Proposal_for_ATA-ACS2.doc

This was never an issue with SSDs.  The requirement comes from
thin-provisioned SCSI disk arrays that would like us to do unmaps
(trims) in units of their internal block size.

There was a huge pushback from the industry about this.  This is clearly
something the array firmware should have to keep track of and not the
operating system.  As a result the unmap granularity size proposal was
pulled and for a while it looked like everything was going to be fine.

Unfortunately yet another array vendor recently discovered that thin
provisioning is hard and sent out a request to have the granularity
brain damage reinstated in the latest protocol draft.

I'm just hoping that all the vendors who came around on the issue will
stay that way...

-- 
Martin K. Petersen	Oracle Linux Engineering