---------- Forwarded message ---------
From: Chris Mason <clm@xxxxxx>
Date: Mon, Jun 22, 2020 at 10:57 AM
Subject: Re: weekly fstrim (still) necessary?
To: David Sterba <dsterba@xxxxxxx>
Cc: Btrfs BTRFS <linux-btrfs@xxxxxxxxxxxxxxx>
On 22 Jun 2020, at 10:23, David Sterba wrote:
On Mon, Jun 22, 2020 at 04:02:34PM +0200, Ulli Horlacher wrote:
On Sun 2020-06-21 (18:57), Chris Murphy wrote:
You need to check fstrim.timer, which in turn triggers
fstrim.service.
root@fex:~# cat /lib/systemd/system/fstrim.timer
root@fex:~# cat /lib/systemd/system/fstrim.service
I'm familiar with the contents of the files. Do you have a
question?
You have deleted my question, it have asked:
This means: an extra fstrim (via btrfsmaintenance script, etc) is
unnecessary?
You need only one service, either from the fstrim or from
btrfsmaintenance.
Dennis’s async discard features are working much better here than
either periodic trims or the traditional mount -o discard. I’d
suggest moving to mount -o discard=async instead.
-chris
Apparently, discard=async is still unsafe on Samsung SSDs, at least
older models. I enabled it on my 850 Pro, and within two days I was
getting uncorrectable errors (for csums). Scrub showed 12,936
uncorrectable errors.
While I was trying to recover, a long SMART analysis showed the
actual
drive to have no errors.
Then, the first recovery attempt failed. I had deleted and recreated
the partition. When I was copying the backup snapshots back to the
SSD, uncorrectable errors showed up, again (4,119 of them after
copying one snapshot). I then overwrote the partition with all
zeros,
and when I copied the snapshots back to it, there were no errors.
After recovering my filesystem, scrub still showed no errors. So,
alls
well that ends well, I guess.
