Date: Thu, 10 Mar 2016 15:45:02 -0800 From: Paul Vixie <paul@redbarn.org> To: Pavel Odintsov <pavel.odintsov@gmail.com> Cc: "freebsd-virtualization@freebsd.org" <freebsd-virtualization@freebsd.org>, Sergei Mamonov <mamonov@fastvps.ru> Subject: Re: ZFS subvolume support inside Bhyve vm Message-ID: <56E206FE.3080000@redbarn.org> In-Reply-To: <CALgsdbcXxAnfkKnU9CuOE-pj0sJJpQ7-XFd6R0bFEeKB-maDRw@mail.gmail.com> References: <CALgsdbcXxAnfkKnU9CuOE-pj0sJJpQ7-XFd6R0bFEeKB-maDRw@mail.gmail.com>
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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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