v.23.8Improvement
Disable Filesystem Cache Update During Backup/Restore
Disable updating the filesystem cache during backup/restore. Filesystem cache must not be updated during backup/restore, it seems it just slows down the process without any profit (because the BACKUP command can read a lot of data and it's no use to put all the data to the filesystem cache and immediately evict it). #52402 (Vitaly Baranov).
Why it matters
DuringBACKUP and RESTORE commands, a large amount of data is read, but updating the filesystem cache with this data is ineffective since it is immediately evicted. Disabling filesystem cache updates prevents unnecessary slowdowns and enhances the overall speed of these operations.How to use it
This optimization is automatically applied internally by ClickHouse duringBACKUP and RESTORE execution. No user action or configuration is required to benefit from this improvement.