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

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