On 04/26 03:29, Rich Freeman wrote: > On Sun, Apr 26, 2020 at 12:15 PM <[email protected]> wrote: > > > > On 04/26 11:20, Rich Freeman wrote: > > > On Sun, Apr 26, 2020 at 10:52 AM <[email protected]> wrote: > > > > > > > > Fstrim reports about 200 GiB of trimmed data. > > > > > > > > > > My suggestion would be to run fstrim twice in a row and see how fast > > > it operates and what the results are. If the second one completes > > > very quickly that suggests that the drive is sane. I'd probably just > > > run it daily in that case, but weekly is probably fine especially if > > > the drive isn't very full. > > > > > > > host:/root>fstrim -v / > > /: 3.3 GiB (3578650624 bytes) trimmed > > host:/root>fstrim -v / > > /: 0 B (0 bytes) trimmed > > > > This time the first fstrim reports a small mount of trimmed > > data and second one no fstrimmed data at all. > > > > Ok, I became a bit less lazy and started looking at the source. > > All fstrim does is send an FITRIM ioctl to the kernel for the device. > This is implemented in a filesystem-dependent manner, and I couldn't > actually find any documentation on it (actual documentation on the > ioctl - not the fstrim manpage/etc). A quick glimpse at the ext4 > source suggests that ext4 has a flag that can track whether a group of > blocks has been trimmed yet or not since it was last deallocated. So > ext4 will make repeated fstrim runs a no-op and the drive won't see > these. > > At least, that was what I got after about 5-10min of browsing. I > didn't take the time to grok how ext4 tracks free space and so on. > > Incidentally, in the other thread the reason that dry-run didn't > report anything to be trimmed is that this is hard-coded: > printf(_("%s: 0 B (dry run) trimmed on %s\n"), path, devname); > https://github.com/karelzak/util-linux/blob/master/sys-utils/fstrim.c#L109 > > Otherwise the ioctl returns how much space was trimmed, and fstrim outputs > this. > > -- > Rich >
Hi Rich, thank you very much for digging into the depth of the sources and for explaining it!!! Very appreciated !!! :) :) To implement a dry run with a printf() is new to me... ;) Cheers! Meino
