Pavel Odintsov wrote:
Hello, Dear Community!
I would like to ask about plans for this storage engine approach. I like
ZFS so much and we are storing about half petabyte of data here.
But when we are speaking about vm's we should use zvols or even raw file
based images and they are discarding all ZFS benefits.
i use zvols for my bhyves and they have two of the most important zfs
advantages:
1. snapshots.
root@mm1:/home/vixie # zfs list|grep fam
zroot1/vms/family 55.7G 3.84T 5.34G -
root@mm1:/home/vixie # zfs snap zroot1/vms/family@before
[family.redbarn:amd64] touch /var/tmp/after
root@mm1:/home/vixie # zfs snap zroot1/vms/family@after
root@mm1:/home/vixie # mkdir /mnt/before /mnt/after
root@mm1:/home/vixie # zfs clone zroot1/vms/family@before zroot1/before
root@mm1:/home/vixie # fsck_ffs -p /dev/zvol/zroot1/beforep2
...
/dev/zvol/zroot1/beforep2: 264283 files, 1118905 used, 11575625 free (28697
frags, 1443366 blocks, 0.2% fragmentation)
root@mm1:/home/vixie # mount -r /dev/zvol/zroot1/beforep2 /mnt/before
root@mm1:/home/vixie # mount -r /dev/zvol/zroot1/beforep2 /mnt/before
root@mm1:/home/vixie # zfs clone zroot1/vms/family@after zroot1/after
root@mm1:/home/vixie # fsck_ffs -p /dev/zvol/zroot1/afterp2
...
/dev/zvol/zroot1/afterp2: 264284 files, 1118905 used, 11575625 free (28697
frags, 1443366 blocks, 0.2% fragmentation)
root@mm1:/home/vixie # mount -r /dev/zvol/zroot1/afterp2 /mnt/after
root@mm1:/home/vixie # ls -l /mnt/{before,after}/var/tmp/after
ls: /mnt/before/var/tmp/after: No such file or directory
-rw-rw-r-- 1 vixie wheel 0 Mar 10 22:52 /mnt/after/var/tmp/after
2. storage redundancy, read caching, and write caching:
root@mm1:/home/vixie # zpool status | tr -d '\t'
pool: zroot1
state: ONLINE
scan: scrub repaired 0 in 2h24m with 0 errors on Thu Mar 10 12:24:13 2016
config:
NAME STATE READ WRITE CKSUM
zroot1 ONLINE 0 0 0
mirror-0 ONLINE 0 0 0
gptid/2427e651-d9cc-11e3-b8a1-002590ea750a ONLINE 0 0 0
gptid/250b0f01-d9cc-11e3-b8a1-002590ea750a ONLINE 0 0 0
mirror-1 ONLINE 0 0 0
gptid/d35bb315-da08-11e3-b17f-002590ea750a ONLINE 0 0 0
gptid/d85ad8be-da08-11e3-b17f-002590ea750a ONLINE 0 0 0
logs
mirror-2 ONLINE 0 0 0
ada0s1 ONLINE 0 0 0
ada1s1 ONLINE 0 0 0
cache
ada0s2 ONLINE 0 0 0
ada1s2 ONLINE 0 0 0
errors: No known data errors
so while i'd love to chroot a bhyve driver to some place in the middle
of the host's file system and then pass VFS right on through, more or
less the way mount_nullfs does, i am pretty comfortable with zvol UFS,
and i think it's misleading to say that zvol UFS lacks all ZFS benefits.
--
P Vixie
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