====== Limit ZFS on Linux Memory Usage ======

<code bash>
echo "options zfs zfs_arc_max=1073741824" >> /etc/modprobe.d/zfs.conf
echo 1073741824 > /sys/module/zfs/parameters/zfs_arc_max
update-initramfs -u
</code>

1073741824 is 1 GiB. It is good to use at most 50 percent (which is the default) of the system memory for ZFS ARC to prevent performance shortage of the host. 

===== Monitoring =====
arcstat.py is located in ''zfsutils-linux'' on Ubuntu.

<code shell-session>
$ apt-file search arcstat.py
zfsutils-linux: /usr/sbin/arcstat.py
</code>

<code shell-session>
# arcstat.py 1
    time  read  miss  miss%  dmis  dm%  pmis  pm%  mmis  mm%  arcsz     c
12:06:55     0     0      0     0    0     0    0     0    0  1005M  1024M
12:06:56    59    10     16    10   16     0    0     0    0  1005M  1024M
12:06:57    68    10     14    10   14     0    0     4   30  1005M  1024M
12:06:58    59    10     16    10   16     0    0     0    0  1005M  1024M
12:06:59    55     6     10     6   10     0    0     0    0  1005M  1024M
</code>

<code shell-session>
# arcstat.py -h
Usage: arcstat.py [-hvx] [-f fields] [-o file] [-s string] [interval [count]]

         -h : Print this help message
         -v : List all possible field headers and definitions
         -x : Print extended stats
         -f : Specify specific fields to print (see -v)
         -o : Redirect output to the specified file
         -s : Override default field separator with custom character or string

Examples:
        arcstat.py -o /tmp/a.log 2 10
        arcstat.py -s "," -o /tmp/a.log 2 10
        arcstat.py -v
        arcstat.py -f time,hit%,dh%,ph%,mh% 1
</code>

===== See Alsos =====
  * https://pve.proxmox.com/wiki/ZFS_on_Linux
  * https://www.solaris-cookbook.eu/linux/linux-ubuntu/debian-ubuntu-centos-zfs-on-linux-zfs-limit-arc-cache/
  * http://fibrevillage.com/storage/169-zfs-arc-on-linux-how-to-set-and-monitor-on-linux

{{tag>zfs zfs-on-linux memory}}