[gentoo-user] SSDs, ext4, fstrim, discard ...

["Stefan G. Weichinger" <lists@xunil.at>]

As mentioned in the systemd-posting I migrated back to an SSD today (on
my main rig, the thinkpad uses an SSD happily for a long time now).

A feature in a local magazine updated my knowledge of how to make use of
the TRIM-command.

It told me not to use the mount-option "discard" anymore, but run fstrim
on the mountpoint frequently.

OK, I learn ;-)

But, AFAI understand, after trimming sectors/bytes on the
filesystem/partition, they should be trimmed. I expect X bytes to be
trimmed at first and if I repeat the command, I expect 0 (or something
pretty low) bytes to be trimmed then, ok?

This is what I wonder about:

~ # fstrim -v /
/: 6195433472 bytes were trimmed
~ # fstrim -v /
/: 6195433472 bytes were trimmed
~ # fstrim -v /
/: 6195433472 bytes were trimmed


I tested it with "discard" on and off.

/ is ext4, yes, and on an SSD, yup.

Do I misunderstand things here?

Thanks, Stefan