Re: discard synchronous on most SSDs?

Martin K. Petersen
2014-03-16T16:22:11Z

>>>>> "Chris" == Chris Samuel <chris@csamuel.org> writes:

Chris> It looks like drives that do support it can be detected with the
Chris> kernel helper function ata_fpdma_dsm_supported() defined in
Chris> include/linux/libata.h.

Chris> I wonder if it would be possible to use that knowledge to extend
Chris> the smartctl's --identify functionality to report this?

Queued trim support is indicated in a log page and not the identify
information. However, we can get to the information we want using
smartctl's ability to look at log pages.

I don't have a single drive from any vendor in the lab that supports
queued trim, not even a prototype. I went out and bought a 840 EVO this
morning because the general lazyweb opinion seemed to indicate that this
drive supports queued trim. Well, it doesn't. At least not in the 120GB
version:

# smartctl -l gplog,0x13 /dev/sda
smartctl 5.43 2012-06-30 r3573 [x86_64-linux-3.14.0-rc6+] (local build)
Copyright (C) 2002-12 by Bruce Allen, http://smartmontools.sourceforge.net

General Purpose Log 0x13 does not exist (override with '-T permissive' option)

If there's a drive with a working queued trim implementation out there,
I'd like to know about it...

--
Martin K. Petersen Oracle Linux Engineering