Re: discard synchronous on most SSDs?

Martin K. Petersen
2014-03-14T19:58:03Z

>>>>> "Marc" == Marc MERLIN <marc@merlins.org> writes:

Marc,

Marc> So I have Sata 3.1, that's great news, it means I can keep using
Marc> discard without worrying about performance and hangs

The fact that the drive reports compliance with a certain version of
SATA does not in any way imply that it implements all commands defined
in that specification.

The location where queued TRIM support is reported is somewhat unusual.
And last I looked hdparm -I had no infrastructure in place to report
stuff contained in log pages.

The kernel does look the right place to determine whether to issue the
queued or unqueued variant or not. But the information isn't exported to
userland.

So right now I'm afraid we don't have a good way for a user to determine
whether a device supports queued trims or not.

I guess we could consider either adding an ATA-specific "I don't suck"
flag in sysfs, add the missing code to hdparm, or both...

--
Martin K. Petersen Oracle Linux Engineering