Il 2022-06-13 10:49 Zhiyong Ye ha scritto:
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?
This is the key point: when first writing to a new chunk, not only it needs to be allocated, but old data must be copied. This r/m/w operation transform an async operation (write) on a sync one (read), ruining performance. Subsequent writes to the same chunk does have the same issue.
The magnitute of the slowdown seems somewhat excessive, though. When dealing with HDD pools, I remember a 3-5x impact on IOPs. Can you show the exact fio command and the parameters of your thin pool (ie: chunk size) and storage subsystem (HDD vs SSD, SATA vs SAS vs NVME)?
Regards. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx GPG public key ID: FF5F32A8 _______________________________________________ linux-lvm mailing list linux-lvm@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
