Stupid question regarding ZFS and `df -h` output
Matthew Seaman
m.seaman at infracaninophile.co.uk
Mon Apr 11 15:12:25 UTC 2016
On 2016/04/10 13:00, Aleksander Alekseev wrote:
> I installed FreeBSD using steps like "Next -> Next -> ZFS -> use entire
> disk and don't bother me with stupid questions -> Next"
>
> I have 128 Gb hard drive:
>
> ada0 at ahcich0 bus 0 scbus0 target 0 lun 0
> ada0: <TOSHIBA THNSNS128GMCP TA4ABBF0> ATA8-ACS SATA 3.x device
> ada0: Serial Number 82GS10GGT2GY
> ada0: 600.000MB/s transfers (SATA 3.x, UDMA6, PIO 8192bytes)
> ada0: Command Queueing enabled
> ada0: 122104MB (250069680 512 byte sectors)
>
> And here is `df -h` output:
>
> Filesystem Size Used Avail Capacity Mounted on
> zroot/ROOT/default 95G 21G 74G 22% /
> devfs 1.0K 1.0K 0B 100% /dev
> zroot/tmp 75G 153M 74G 0% /tmp
> zroot/usr/home 89G 15G 74G 17% /usr/home
> zroot/usr/ports 75G 859M 74G 1% /usr/ports
> zroot/usr/src 76G 1.2G 74G 2% /usr/src
> zroot/var/audit 74G 96K 74G 0% /var/audit
> zroot/var/crash 75G 930M 74G 1% /var/crash
> zroot/var/log 74G 360K 74G 0% /var/log
> zroot/var/mail 74G 188K 74G 0% /var/mail
> zroot/var/tmp 74G 136K 74G 0% /var/tmp
> zroot 74G 96K 74G 0% /zroot
>
> How exactly should I read this to get result "all 128 GB are used"?
I take it you mean 'what would this output look like if all 128GB were
used'? Because at the moment, you've got quite a lot of your disk
spaces still unused.
The 'Avail' column would show zero or a very small amount of space
available when the pool was full, and the figures for the 'Size' and
'Used' columns would have pretty near equal values.
The 'Size' and 'Capacity' columns are a bit weird in ZFS -- unlike a
system with fixed size filesystems where the meaning of those columns is
clear, with ZFS 'Size' means "The sum of the already used space for
this ZFS plus all of the available space in the entire pool"[*] -- so
'Size' for one ZFS will change as data is added to another ZFS.
Capacity is just the ratio of 'Used' over 'Size', and shows similar effects.
Cheers,
Matthew
[*] Assuming that there haven't been any reservations or size limits
configured for that ZFS, which is generally the case for what the
installer creates.
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