[linux-lvm] Why doesn't the lvmcache support the discard (trim) command?
Ilia Zykov
linux at izyk.ru
Thu Oct 18 22:56:04 UTC 2018
Maybe it will be implemented later? But it seems to me a little strange when there is no way to clear the cache from a garbage.
Maybe I do not understand? Can you please explain this behavior.
For example:
I have the full cached partition, with full cache:
[root at localhost ~]# df -h /data
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/test-data 12G 12G 0 100% /data
[root at localhost ~]# lvs -a
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
data test Cwi-aoC--- 12.00g [fast] [data_corig] 99.72 2.93 0.00
[data_corig] test owi-aoC--- 12.00g
[fast] test Cwi---C--- 1.00g 99.72 2.93 0.00
[fast_cdata] test Cwi-ao---- 1.00g
[fast_cmeta] test ewi-ao---- 8.00m
[lvol0_pmspare] test ewi------- 8.00m
I clear the partition and do fstrim:
[root at localhost ~]# rm -rf /data/*
[root at localhost ~]# fstrim -v /data
[root at localhost ~]# df -h /data
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/test-data 12G 41M 12G 1% /data
But the cache remained full:
[root at localhost ~]# lvs -a
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
data test Cwi-aoC--- 12.00g [fast] [data_corig] 99.72 2.93 0.00
[data_corig] test owi-aoC--- 12.00g
[fast] test Cwi---C--- 1.00g 99.72 2.93 0.00
[fast_cdata] test Cwi-ao---- 1.00g
[fast_cmeta] test ewi-ao---- 8.00m
[lvol0_pmspare] test ewi------- 8.00m
Thank you.
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