Can FreeBSD boot from a pool comprised of multiple vdevs?
Matt Reimer
not, what would it take to get it working?
I got 8.0-BETA4 booting from a pool comprised of a single raidz vdev,
but when I added another raidz vdev it fails to boot with this error:
ZFS: i/o error - all block copies unavailable
ZFS: can't read object set for dataset lld
Can't find root filesystem - giving up
ZFS: unexpected object set type lld
ZFS: unexpected object set type lld
FreeBSD/i386 boot
Default: glamdring:/boot/kernel/kernel
boot:
ZFS: unexpected object set type lld
(Apparently loader's printf() doesn't understand %lld.)
Boots successfully with gptzfsboot:
# zpool status
pool: glamdring
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
glamdring ONLINE 0 0 0
raidz1 ONLINE 0 0 0
label/glamdring-0.0 ONLINE 0 0 0
label/glamdring-0.1 ONLINE 0 0 0
label/glamdring-0.2 ONLINE 0 0 0
errors: No known data errors
Does not boot:
# zpool status
pool: glamdring
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
glamdring ONLINE 0 0 0
raidz1 ONLINE 0 0 0
label/glamdring-0.0 ONLINE 0 0 0
label/glamdring-0.1 ONLINE 0 0 0
label/glamdring-0.2 ONLINE 0 0 0
raidz1 ONLINE 0 0 0
label/glamdring-1.0 ONLINE 0 0 0
label/glamdring-1.1 ONLINE 0 0 0
label/glamdring-1.2 ONLINE 0 0 0
errors: No known data errors
Thanks in advance.
Matt
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Artem Belevich
I've just spent a bit of time investigating the same issue.
There was a thread on -current in June that discussed ZFS booting
issue and this email suggested that zfsboot does not support gang
blocks.
http://lists.freebsd.org/pipermail/freebsd-current/2009-June/008589.html
If I understand it correctly, gang blocks are used when ZFS can't (or
does not want to) allocate contiguous block of required size, so the
block is split in sub-blocks that in turn may be gang blocks. I.e.
we're looking at a tree of blocks. If that's indeed the case, it
implies that even on a single-disk system we may eventually run into a
situation when newly installed kernel will be written using gang block
and thus would not be handled correctly by zfsboot.
That said, I've tried many possible combinations on a VirtualBox
running 8.0BETA4 and most of them didn't work. Here's the summary:
Zpool configurations I was able to boot from:
* 1 disk
* 1 mirror of 2 disks
* 2 mirrors of 2 disks each
* 2-disk raidz (kind of pointless, but..)
Configurations that didn't work:
* RAIDZ2 with 8 disks
* RAIDZ2 with 4 disks
* RAIDZ2 with 3 disks
* RAIDZ with 8 disks
* RAIDZ with 3 disks
* 4 mirrors of 2 disks each
* 3 mirrors of 3 disks each.
Usually gptzfsboot complains that it can't read MOS. Striped
multi-disk setups resulted in "can't find dsl_dir".
I did some digging in case of RAIDZ2 booting failure and it does look
that the failure happens because calculated checksum does not match
expected one. Due to lack of my ZFS knowlegde I didn't get deeper than
that.
--Artem