[linux-lvm] Why is the performance of my lvmthin snapshot so poor

Gionatan Danti g.danti at assyoma.it
Tue Jun 14 12:56:30 UTC 2022

Il 2022-06-14 12:16 Zhiyong Ye ha scritto:
> After creating the PV and VG based on the iSCSI device, I created the
> thin pool as follows:
> lvcreate -n pool -L 1000G test-vg
> lvcreate -n poolmeta -L 100G test-vg
> lvconvert --type thin-pool --chunksize 64k --poolmetadata
> test-vg/poolmeta test-vg/pool
> lvchange -Z n test-vg/pool

I did my performance test with bigger chunk size, in the range of 
128-512K. It can very well be that the overload of a smaller chunk size 
results in 10x lower IOPs for to-be-allocated-and-copied chunks. Can you 
retry fio after increasing chunk size?

As a side not, if I remember correcly thin pool metadata is hard limited 
do 16 GB - no need to allocate 100 GB for it.

Danti Gionatan
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