From 2172bbb2be214d0e0c9a25867712d30802c153dd Mon Sep 17 00:00:00 2001 From: Christoph Heiss Date: Tue, 5 Mar 2024 13:13:00 +0100 Subject: [PATCH] local-zfs: mention `zfs_arc_max` clamping by the installer This was forgotten to be updated when it changed it the installer and now reported in the forum [0] that the docs are a bit outdated in this regard. [0] https://forum.proxmox.com/threads/hat-proxmox-8-neue-zfs_arc_max-settings.142754/ Signed-off-by: Christoph Heiss --- local-zfs.adoc | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/local-zfs.adoc b/local-zfs.adoc index 718b737..25af423 100644 --- a/local-zfs.adoc +++ b/local-zfs.adoc @@ -570,11 +570,16 @@ Limit ZFS Memory Usage ~~~~~~~~~~~~~~~~~~~~~~ ZFS uses '50 %' of the host memory for the **A**daptive **R**eplacement -**C**ache (ARC) by default. Allocating enough memory for the ARC is crucial for -IO performance, so reduce it with caution. As a general rule of thumb, allocate -at least +2 GiB Base + 1 GiB/TiB-Storage+. For example, if you have a pool with -+8 TiB+ of available storage space then you should use +10 GiB+ of memory for -the ARC. +**C**ache (ARC) by default. For new installations starting with {pve} 8.1, the +ARC usage limit will be set to '10 %' of the installed physical memory, clamped +to a maximum of +16 GiB+. This value is written to `/etc/modprobe.d/zfs.conf`. + +Allocating enough memory for the ARC is crucial for IO performance, so reduce it +with caution. As a general rule of thumb, allocate at least +2 GiB Base + 1 +GiB/TiB-Storage+. For example, if you have a pool with +8 TiB+ of available +storage space then you should use +10 GiB+ of memory for the ARC. + +ZFS also enforces a minimum value of +64 MiB+. You can change the ARC usage limit for the current boot (a reboot resets this change again) by writing to the +zfs_arc_max+ module parameter directly: @@ -583,8 +588,8 @@ change again) by writing to the +zfs_arc_max+ module parameter directly: echo "$[10 * 1024*1024*1024]" >/sys/module/zfs/parameters/zfs_arc_max ---- -To *permanently change* the ARC limits, add the following line to -`/etc/modprobe.d/zfs.conf`: +To *permanently change* the ARC limits, add (or change if already present) the +following line to `/etc/modprobe.d/zfs.conf`: -------- options zfs zfs_arc_max=8589934592