Dne 29. 12. 23 v 1:48 Mikhail Morfikov napsal(a):
I've got the following setup: LUKSv2+LVM on an SSD drive, and I have
trim/discad enabled
for encrypted container. I also use e2scrub for Online ext4 Metadata Check
which uses a 4
GiB LVM snapshot. I currently have 10 logical volumes, which are periodically
(once a week)
scanned for errors. I've got a question concerning the *issue_discards* option
that can be
specified in the /etc/lvm/lvm.conf file. What actually happens when this
option is enabled
and the LVM snapshot is removed after fsck finishes its job? Will the whole 4
GiB be erased
on the flash? Is it safe to enable this option in such case, or is it better
to leave it
disabled?
Hello
issue_discards is relevant only when you *REMOVE* LVs - the free space in VG
is after such removal 'discarded' - which is only useful in case you i.e.
pay for 'provisioned' space for your VG (or you have some very very very old
ssd) - so this will make you VG space consumption smaller - but it will also
make restoring of accidentally removed LVs impossible as the recovered LV will
be simply just an empty disk space.
So for 100% you don't need to enabled it for e2scrub as discards are normally
passed through to your LV device as you may easily check in your sysfs dir:
/sys/block/XXXX/queue/discard_max_bytes
Regards
Zdenek
