[lustre-discuss] ZFS tuning for MDT/MGS

Degremont, Aurelien degremoa at amazon.com
Tue Mar 19 11:46:53 PDT 2019

Also, if you’re not using Lustre 2.11 or 2.12, do not forget dnodesize=auto and recordsize=1M for OST

zfs set dnodesize=auto mdt0
zfs set dnodesize=auto ostX


(useful for 2.10 LTS. Automatically done by Lustre for 2.11+)

De : lustre-discuss <lustre-discuss-bounces at lists.lustre.org> au nom de "Carlson, Timothy S" <Timothy.Carlson at pnnl.gov>
Date : mercredi 13 mars 2019 à 23:07
À : Riccardo Veraldi <Riccardo.Veraldi at cnaf.infn.it>, Kurt Strosahl <strosahl at jlab.org>, "lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
Objet : Re: [lustre-discuss] ZFS tuning for MDT/MGS

+1 on

options zfs zfs_prefetch_disable=1

Might not be as critical now, but that was a must-have on Lustre 2.5.x


From: lustre-discuss <lustre-discuss-bounces at lists.lustre.org> On Behalf Of Riccardo Veraldi
Sent: Wednesday, March 13, 2019 3:00 PM
To: Kurt Strosahl <strosahl at jlab.org>; lustre-discuss at lists.lustre.org
Subject: Re: [lustre-discuss] ZFS tuning for MDT/MGS

these are the zfs settings I use on my MDSes

 zfs set mountpoint=none mdt0
 zfs set sync=disabled mdt0
 zfs set atime=off amdt0
 zfs set redundant_metadata=most mdt0
 zfs set xattr=sa mdt0

if youor MDT partition is on a 4KB sector disk then you can use ashift=12 when you create the filesystem but zfs is pretty smart and in my case it recognized it automatically and used ashift=12 automatically.

also here are the zfs kernel modules parameters i use to ahve better performance. I use it on both MDS and OSSes

options zfs zfs_prefetch_disable=1
options zfs zfs_txg_history=120
options zfs metaslab_debug_unload=1
options zfs zfs_vdev_scheduler=deadline
options zfs zfs_vdev_async_write_active_min_dirty_percent=20
options zfs zfs_vdev_scrub_min_active=48
options zfs zfs_vdev_scrub_max_active=128
#options zfs zfs_vdev_sync_write_min_active=64
#options zfs zfs_vdev_sync_write_max_active=128
options zfs zfs_vdev_sync_write_min_active=8
options zfs zfs_vdev_sync_write_max_active=32
options zfs zfs_vdev_sync_read_min_active=8
options zfs zfs_vdev_sync_read_max_active=32
options zfs zfs_vdev_async_read_min_active=8
options zfs zfs_vdev_async_read_max_active=32
options zfs zfs_top_maxinflight=320
options zfs zfs_txg_timeout=30
options zfs zfs_dirty_data_max_percent=40
options zfs zfs_vdev_async_write_min_active=8
options zfs zfs_vdev_async_write_max_active=32

some people may disagree with me anyway after years of trying different options I reached this stable configuration.

then there are a bunch of other important Lustre level optimizations that you can do if you are looking for performance increase.



On 3/13/19 11:44 AM, Kurt Strosahl wrote:

Good Afternoon,

    I'm reviewing the zfs parameters for a new metadata system and I was looking to see if anyone had examples (good or bad) of zfs parameters?  I'm assuming that the MDT won't benefit from a recordsize of 1MB, and I've already set the ashift to 12.  I'm using an MDT/MGS made up of a stripe across mirrored ssds.




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