zfs newbie

[Doug McIntyre]

On Tue, Sep 07, 2021 at 06:17:45PM -0400, Doug Denault wrote:
> Following the default 12.2 zfs install I got one pool (zroot) and a dataset for 
> each of the traditional mount points. So zfs list shows:
> 
> NAME                 USED  AVAIL  REFER  MOUNTPOINT
> zroot                279G  6.75T    88K  /zroot
> zroot/ROOT          1.74G  6.75T    88K  none
> zroot/ROOT/default  1.74G  6.75T  1.74G  /
> zroot/tmp            176K  6.75T   176K  /tmp
> zroot/usr            277G  6.75T    88K  /usr
> zroot/usr/home       276G  6.75T   276G  /usr/home
> zroot/usr/ports       88K  6.75T    88K  /usr/ports
> zroot/usr/src        670M  6.75T   670M  /usr/src
> zroot/var           47.5M  6.75T    88K  /var
> zroot/var/audit       88K  6.75T    88K  /var/audit
> zroot/var/crash       88K  6.75T    88K  /var/crash
> zroot/var/log        820K  6.75T   820K  /var/log
> zroot/var/mail      46.3M  6.75T  46.3M  /var/mail
> zroot/var/tmp         88K  6.75T    88K  /var/tmp
..
> From a sysadmin view I rather like the multiple datasets. Are there advantages 
> to one over the other?

One huge one I use all the time... You can set quotas per dataset.
For me, /var/log gets 4G (typically). Depending on the usecase, /tmp and /var/tmp may get
quotas, but I wouldn't go blindly do that. 

Other things you can do is if you carve your database storage out of zroot, then you
can set tuned ZFS parameters for your database file system areas. (ie. blocksize
matching, compression/dedup setup, etc).