Re: Why is the performance of my lvmthin snapshot so poor
Gionatan Danti <[email protected]>
| Newsgroups | gmane.linux.lvm.general |
|---|---|
| Message-ID | <[email protected]> |
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: [email protected] - [email protected] GPG public key ID: FF5F32A8 _______________________________________________ linux-lvm mailing list [email protected] https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/