ZFS Tunables for Lustre Metadata Servers (MDS) - Revision history

Snehring: Remove some older options, update.

2026-10-19T20:00:38Z

Remove some older options, update.

← Older revision		Revision as of 12:00, 19 October 2026
Line 7:		Line 7:
	\|-		\|-
	\|zfs_arc_max		\|zfs_arc_max
	\|Maximum size of the ARC.		\|Maximum size of the ARC in bytes.
	\|50% RAM		\|0 (~50% RAM)
	\|75% RAM		\|75% RAM
	\|-		\|-
	\|~~zfs_arc_meta_limit~~		\|zfs_arc_meta_balance
	\|Increasing this value ~~will~~ improve performance if the workload ~~involves operations on a large number of files and directories, or frequent~~ metadata ~~operations~~, at the cost of less file data fitting in the ARC.		\|Increasing this value can improve performance if the workload is metadata-op heavy, at the cost of less file data fitting in the ARC. The default of 500 would prefer metadata 5x over data.
	\|~~25% ARC~~		\|500
	~~\|75% ARC~~		\|500+
	\|-
	~~\|zfs_vdev_scheduler~~
	~~\|VDEV scheduler~~
	~~\|noop~~
	\|~~Deadline~~
	\|-		\|-
	\|metaslab_debug_unload		\|metaslab_debug_unload
	\|This option prevents ZFS from unloading the spacemaps from a metaslab once it is read in.		\|This option prevents ZFS from unloading the spacemaps from a metaslab once it is read in. Unless you've noticed significant overhead from loading in spacemaps, you probably don't need this.
	\|0		\|0
	\|1		\|1
			\|-
	\|}		\|}

	For a comprehensive description of all available ZFS ~~and SPL~~ module parameters, refer to the [https://github.~~com~~/~~zfsonlinux/zfs/blob/master/man/man5/zfs-module~~-~~parameters.5 zfs-module-parameters](5) and [https:~~//~~github~~.~~com/zfsonlinux/spl/blob/master/man/man5/spl-module-parameters.5 spl-~~module-parameters]~~(5) man pages~~.
			For a comprehensive description of all available ZFS module parameters, refer to the [https://openzfs.github.io/openzfs-docs/Performance%20and%20Tuning/Module%20Parameters.html module parameters] docs.

	[[Category:ZFS OSD Tuning]]		[[Category:ZFS OSD Tuning]]
	[[Category:Lustre Systems Administration]]		[[Category:Lustre Systems Administration]]

Adilger: remove spl_kmem_cache_slab_limit since this is only recommending to leave the value at the default

2018-05-25T22:22:22Z

remove spl_kmem_cache_slab_limit since this is only recommending to leave the value at the default

← Older revision		Revision as of 14:22, 25 May 2018
Line 25:		Line 25:
	\|0		\|0
	\|1		\|1
	\|-
	~~\|spl_kmem_cache_slab_limit~~
	\|Objects of spl_kmem_cache_slab_limit or smaller will be allocated using the Linux slab allocator, large objects use the SPL allocator. A cut-off of 16K was determined to be optimal for architectures using 4K pages.
	~~\|16384~~
	~~\|16384~~
	\|}		\|}

Malcolm at 05:53, 31 August 2017

2017-08-31T05:53:30Z

← Older revision		Revision as of 21:53, 30 August 2017
Line 35:		Line 35:

	[[Category:ZFS OSD Tuning]]		[[Category:ZFS OSD Tuning]]
			[[Category:Lustre Systems Administration]]

Malcolm at 01:55, 30 August 2017

2017-08-30T01:55:16Z

← Older revision		Revision as of 17:55, 29 August 2017
Line 31:		Line 31:
	\|16384		\|16384
	\|}		\|}

			For a comprehensive description of all available ZFS and SPL module parameters, refer to the [https://github.com/zfsonlinux/zfs/blob/master/man/man5/zfs-module-parameters.5 zfs-module-parameters](5) and [https://github.com/zfsonlinux/spl/blob/master/man/man5/spl-module-parameters.5 spl-module-parameters](5) man pages.

	[[Category:ZFS OSD Tuning]]		[[Category:ZFS OSD Tuning]]

Malcolm: Created page with " {| class="wikitable" style="text-align:left;" !Parameter !Notes !Default !Suggested |- |zfs_arc_max |Maximum size of the ARC. |50% RAM |75% RAM |- |zfs_arc_meta_limit |Increa..."

2017-08-14T08:29:22Z

Created page with " {| class="wikitable" style="text-align:left;" !Parameter !Notes !Default !Suggested |- |zfs_arc_max |Maximum size of the ARC. |50% RAM |75% RAM |- |zfs_arc_meta_limit |Increa..."

New page

{| class="wikitable" style="text-align:left;"
!Parameter
!Notes
!Default
!Suggested
|-
|zfs_arc_max
|Maximum size of the ARC.
|50% RAM
|75% RAM
|-
|zfs_arc_meta_limit
|Increasing this value will improve performance if the workload involves operations on a large number of files and directories, or frequent metadata operations, at the cost of less file data fitting in the ARC.
|25% ARC
|75% ARC
|-
|zfs_vdev_scheduler
|VDEV scheduler
|noop
|Deadline
|-
|metaslab_debug_unload
|This option prevents ZFS from unloading the spacemaps from a metaslab once it is read in.
|0
|1
|-
|spl_kmem_cache_slab_limit
|Objects of spl_kmem_cache_slab_limit or smaller will be allocated using the Linux slab allocator, large objects use the SPL allocator. A cut-off of 16K was determined to be optimal for architectures using 4K pages.
|16384
|16384
|}

[[Category:ZFS OSD Tuning]]