Re: ZFS: amd64, devd, root file system.

On Sat, Apr 14, 2007 at 10:03:12PM +0200, Stefan Esser wrote:
Pawel Jakub Dawidek wrote:
On Sat, Apr 14, 2007 at 11:21:37AM +0200, Stefan Esser wrote:
It is amazingly simple to get a test setup going and it worked fine
in my initial simple test cases. But now I've run into problems that
probably are not technical but caused by a lack of understanding ...

This is not the first report that it doesn't work as it should. One was
that /boot/defaults/loader.conf wasn't fresh enough, and there were no:

Hi Pawel,

thanks for the reply, I got it working with some effort, see below ...

zpool_cache_load="YES"

This is apparently implied by zfs_load="YES" and redundant.

No, it isn't. It is absolutely necessary.

zpool_cache_type="/boot/zfs/zpool.cache"
zpool_cache_name="/boot/zfs/zpool.cache"

These are defined in /boot/defaults/loader.conf ...

zpool_cache_load="YES" should be as well. I hope you didn't change it.
You should not need to touch /boot/defaults/loader.conf.

This could be fixed by exporting and then importing the pool (with -f).
There after the pool could be mounted and I could manually set up the
complete file system hierarchy. I verified that "/boot/zfs/zpool.cache"
was updated during the import (written to the boot partition), but the
next reboot failed again and I again got the same error status as shown
above.

Are you sure the updated file is the same file which is loaded on boot?

I made an attempt to fix it by creating another pool on an (during the
tests) unused swap partition on my "normal" UFS system disk (which I
had made an IDE slave for these tests). After copying the necessary
files over to the newly created "test2" pool on the SWAP partition I
got a system that mounted "zfs:test2" and that just worked ...

Not working: zpool create test ad0s2
Working: zpool create test2 ad1s1b

(I.e. "test2" could be mounted automatically, while "test" required me
to boot with an UFS root and to export/import the pool before it could
be manually mounted.)

Well, after some more testing I destroyed the pool "test" and created
it on "ad0s2c" instead of "ad0s2", and voila, I had my problem solved.

It appears, that a zpool can be manually mounted if it resides on ad0s2,
but in order to make the kernel accept it during boot, it must be in a
BSD partition. Does that make sense? (I did not want to try again with
another pool in a slice, since I did not want to give up what I had just
achieved with so much effort ;-)

I'm sorry, but it doesn't make sense at all:) All GEOM providers should
be equal for ZFS, no matter if this is disk, slice, partition, mirror,
encrypted provider or anything else.

Do I need fstab entries for for ZFS file systems (e.g. "test/usr")
or does ZFS mount them automatically when the pool "test" is mounted?

They are mount via rc.d/zfs script.

Oh well, I should have looked there instead of asking ;-)
Hmmm, I assume that "zfs mount -a" will ignore file systems that are
marked as "legacy", and those will instead mounted together with other
local file systems?

That's right.

For now only exports file. zpool.cache use to be there as well, but we
need it in /boot/zfs/ to be able to have root-on-ZFS.

Yes, I see. It might be useful to make zpool.cache available in /etc/zfs
via a symlink, but this might also cause confusion or inconsistencies
and I see good reasons to maintain that file in /boot/zfs.

Hmm? What for do you need zpool.cache in /etc/zfs/? This file is for ZFS
internal use only, I see no reason to symlink it or do anything with it.
ZFS should work in the way that you shouldn't even know it exists and we
should be moving into that direction:)

Ok, it took me quite a few hours to get ZFS installed the way I wanted
it, and it seems that ad0s2 and ad0s2c are quite different with regard
to their suitability to hold ZFS pools. Was this to be expected?

Or is the diagnosis wrong and something else is responsible that it
works for me, now?

I don't know what was the reason, but ad0s2/ad0s2c should make no
difference...

--
Pawel Jakub Dawidek http://www.wheel.pl
pjd@xxxxxxxxxxx http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!

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