Hi all,
I am new to lvmthin. When I created snapshots using lvmthin, the write
performance of the original lvm was poor.
After I create thin lv with zeroing disabled, I first write the whole
volume with fio, then create snapshot, and finally test the write
performance of this volume with fio again. The performance after
creating a snapshot is very poor, only 10% of the thick lv, and also
much worse than the performance of the first write of thin lv. The
performance data for random writes in my environment fio is as follows:
case iops
thick lv 63043
thin lv 42130
snapshotted thin lv 5245
It is mentioned in the lvmthin main page under "Chunk size" that the
size of chunksize has an impact on snapshot performance. So I tested the
write performance after creating snapshots with different chunksize. The
data is shown below:
chunksize iops
64k 5245
256k 2115
1024k 509
The performance degradation after snapshotting is expected as writing to
a snapshotted lv involving reading the original data, writing it
elsewhere and then writing new data into the original chunk. But the
performance loss was so much more than I expected. Is there any way to
improve performance after creating a snapshot? Can I ask for your help?
Regards,
Zhiyong Ye
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