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Chapter 24. Writeback Throttle

Ceph replicates some of the writeback behavior in the kernel, because the page cache tends to keep dirty data round too long.

filestore_wbthrottle_enable

Description
Enables the filestore writeback throttle. The filestore writeback throttle is used to prevent large amounts of uncommitted data from building up before each filestore sync. (Experts only).
Type
Boolean
Default
true

filestore_wbthrottle_btrfs_bytes_start_flusher

Description
Dirty bytes threshold at which Ceph begins background flushing for btrfs.
Type
64-bit Unsigned Integer
Default
41943040

filestore_wbthrottle_btrfs_bytes_hard_limit

Description
Dirty bytes threshold at which Ceph begins to throttle I/O until the flusher catches up for btrfs.
Type
64-bit Unsigned Integer
Default
419430400

filestore_wbthrottle_btrfs_ios_start_flusher

Description
Dirty ios threshhold at which Ceph begins background flushing for btrfs.
Type
64-bit Unsigned Integer
Default
500

filestore_wbthrottle_btrfs_ios_hard_limit

Description
Dirty ios threshhold at which Ceph begins to throttle IO until the flusher catches up for btrfs.
Type
64-bit Unsigned Integer
Default
5000

filestore_wbthrottle_btrfs_inodes_start_flusher

Description
Dirty inodes threshhold at which Ceph begins background flushing for btrfs.
Type
64-bit Unsigned Integer
Default
500

filestore_wbthrottle_btrfs_inodes_hard_limit

Description
Dirty inodes threshhold at which Ceph begins to throttle IO until the flusher catches up for btrfs. Must be less than the fd limit.
Type
64-bit Unsigned Integer
Default
5000

filestore_wbthrottle_xfs_bytes_start_flusher

Description
Dirty bytes threshold at which Ceph begins background flushing for XFS.
Type
64-bit Unsigned Integer
Default
41943040

filestore_wbthrottle_xfs_bytes_hard_limit

Description
Dirty bytes threshold at which Ceph begins to throttle IO until the flusher catches up for XFS.
Type
64-bit Unsigned Integer
Default
419430400

filestore_wbthrottle_xfs_ios_start_flusher

Description
Dirty ios threshhold at which Ceph begins background flushing for XFS.
Type
64-bit Unsigned Integer
Default
500

filestore_wbthrottle_xfs_ios_hard_limit

Description
Dirty ios threshhold at which Ceph begins to throttle IO until the flusher catches up for XFS.
Type
64-bit Unsigned Integer
Default
5000

filestore_wbthrottle_xfs_inodes_start_flusher

Description
Dirty inodes threshhold at which Ceph begins background flushing for XFS.
Type
64-bit Unsigned Integer
Default
500

filestore_wbthrottle_xfs_inodes_hard_limit

Description
Dirty inodes threshhold at which Ceph begins to throttle IO until the flusher catches up for XFS. Must be less than the fd limit.
Type
64-bit Unsigned Integer
Default
5000