Dne 30. 04. 24 v 19:54 Michael DiDomenico napsal(a):
this is probably expected behavior, but i'd like to confirm as i'm not a device-mapper expert we're using COW snapshots overtop of a readonly block device. this seems to be working fine, however, when a person deletes files the blocks are not freed. case in point a RO block device with a COW filled up to 100% as shown in df. when i deleted some files to free space the usage never decreased to create the mount we do echo "0 <realsize> linear /dev/loop1 0" | dmsetup create roimage-base-real echo "0 <cowsize> linear /dev/loop2 0" | dmsetup create roimage-snap-cow echo "0 <realsize> snapshot-origin /dev/mapper/roimage-base-real" | dmsetup create roimage-base echo "0 <realsize> snapshot /dev/mapper/roimage-base-real /dev/mapper/roimage-snap-cow n 1" | dmsetup create roimage-cow mount /dev/mapper/roimage-cow /roimagemntpnt this is working as the origin device is Read-Only, but we can change files. so two questions come up 1 when we delete files, how do we reclaim the space 2 should/can we roll the snapshots to reclaim space?
Please consider using thin-pools - this should be giving you the features you are likely looking for.
Note - you can use thin-pool to hold only snapshots and use your read-only volume as the external origin for thin volume.
Regards Zdenek
