Block layer discard requests [LWN.net]

Block layer discard requests

Posted Aug 14, 2008 15:58 UTC (Thu) by bronson (subscriber, #4806)
Parent article: Block layer discard requests

This sounds like a most needed addition.  I'll be watching its development.

Quick question: why the terminology change?  If T13 calls it "trim", why should Linux call it
"discard"?

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Block layer discard requests

Posted Aug 14, 2008 17:34 UTC (Thu) by willy (subscriber, #9762) [Link] (2 responses)

SCSI calls it PUNCH.  I dread to think what the Flash people call it.  Names change in
different standards.

Block layer discard requests

Posted Aug 15, 2008 11:39 UTC (Fri) by dougg (guest, #1894) [Link] (1 responses)

Poking around the latest ATA8-ACS and SCSI drafts I can find no sign of the ATA TRIM command
(in D1699r6-ATA8-ACS.pdf). Willy, could you give a document reference.

As for the SCSI PUNCH command that is in the Object Storage Devices (OSD-2) command set. No
wonder it is complex with a 236 byte cdb! Is OSD appropriate for flash devices? [Sledge hammer
for an acorn.] Surely a new SCSI command is needed in SBC-3 (SCSI Block Commands as used by
disks today) and the command name "TRIM" hasn't been used yet.

Also, there are the SCSI to ATA Translation (SAT) PASS-THROUGH commands that allow, for
example, a ATA TRIM command to be tunnelled through a SCSI command layer.

Block layer discard requests

Posted Aug 15, 2008 14:52 UTC (Fri) by willy (subscriber, #9762) [Link]

The proposals I'm looking at are
http://www.t13.org/Documents/UploadedDocuments/docs2008/e... and http://www.t10.org/ftp/t10/document.08/08-149r0.pdf
I think this PUNCH is different from the PUNCH you're looking at in OSD2.