ZFS (and quota)

Johan Ström johan at stromnet.se
Wed Sep 19 15:56:11 PDT 2007


I just installed FreeBSD-current on a box (actually upgraded 6.2 to - 
current) to experiment a bit.
I was playing around with ZFS a bit and tried out the quota features.  
While doing this I noticed that it doesnt seem like you get a "disk  
full" notice the same way as you do on a "normal" (UFS) filesystem.  
Instead of aborting the operation with "No space left on device" it  
just continued:

[root at devbox ~]# zpool create tank /dev/ad2
[root at devbox ~]# zpool list
NAME                    SIZE    USED   AVAIL    CAP  HEALTH     ALTROOT
tank                   37.2G    111K   37.2G     0%  ONLINE     -

[root at devbox /tank]# zfs create -V 10M tank/set3vol
[root at devbox /tank]# newfs /dev/zvol/tank/set3vol
/dev/zvol/tank/set3vol: 10.0MB (20480 sectors) block size 16384,  
fragment size 2048
         using 4 cylinder groups of 2.52MB, 161 blks, 384 inodes.
super-block backups (for fsck -b #) at:
160, 5312, 10464, 15616
[root at devbox /tank]# mount /dev/zvol/tank/set3vol set3vol/
[root at devbox /tank]# cd set3vol/
[root at devbox /tank/set3vol]# dd if=/dev/urandom of=test

/tank/set3vol: write failed, filesystem is full
dd: test: No space left on device
19169+0 records in
19168+0 records out
9814016 bytes transferred in 2.276896 secs (4310261 bytes/sec)
[root at devbox /tank]# zfs create tank/set2
[root at devbox /tank/set2]# zfs set quota=10M tank/set2
[root at devbox /tank/set2]# zfs get quota tank/set2
tank/set2  quota     10M        local
[root at devbox /tank/set2]# dd if=/dev/urandom of=test
18563+0 records in
18562+0 records out
9503744 bytes transferred in 199.564353 secs (47622 bytes/sec)
[root at devbox /tank/set2]# zfs list tank/set2
tank/set2  9.15M   870K  9.15M  /tank/set2

No hard stop there, it just tries to write more and more and more..  
Well the quota is enforced fine but shouldnt there be some more hard  
error? I'm not sure how regular UFS quotas work though since I never  
used them, but this seems like strange behaviour.

Anyway, how "stable" is the ZFS support and -current / Fbsd7 in  
general now? I'm about to get a new server, 8 core xeon thingy with  
lots of disk, so I would probably benifit very much from running  
freebsd-7 (much better multicore performance if i've understood  
correct). Beeing able to use ZFS for some of my jails would rock too,  
having individual quotas and all the other flexibilitys ZFS provides  
(ie creating a new set for every jail and enforce individual quota)..  
Would anyone dare to do this on a production machine yet? Is anyone  
doing it?

Well, it can't be said to many times, keep up the good work! Thanks  
all fbsd developers (and others too!) :)

Johan Ström
johan at stromnet.se

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