9.0 install and journaling

Da Rock freebsd-questions at herveybayaustralia.com.au
Tue Dec 13 00:06:15 UTC 2011

On 12/13/11 04:09, RW wrote:
> On Sun, 11 Dec 2011 15:42:52 +1000
> Da Rock wrote:
>> On 12/11/11 10:23, RW wrote:
>>> On Sun, 11 Dec 2011 08:17:41 +1000
>>> Da Rock wrote:
>>>>> SUJ speeds up the check a lot, seconds as opposed to minutes.  If
>>>>> something happens to the journal, it falls back to a standard
>>>>> fsck.
>>>> But fsck needs to be run manually- I have users that can't do that,
>>>> and the filesystem corrupts. Ergo gjournal; it boots up and fixes
>>>> on the fly. So SU+J needs a manual fsck before booting proper or
>>>> can it just boot and be done?
>>> It's not very different; gjournal and SU both attempt to leave the
>>> filesystem in an coherent state, but both still need a preen to
>>> recover lost space. In either case the preen can fail requiring a
>>> full fsck.
>>> Journalled SU make SU behave more like gjournal in that you can do a
>>> fast foreground check which avoids the lengthy background fsck and
>>> avoids deferring the handling of unexpected inconsistencies to the
>>> next boot.
>> Yes, but I don't do a fsck to recover gjournal- it has a miniscule
>> blurp for a nanosecond and prints a message at boot and thats it.
> If the filesystem is mounted via fstab the fsck is normally done
> automatically. You may not have noticed this because if nothing needs
> doing fsck_ufs can mark a gjournal filesystem clean instantaneously.
> There are two other possibilities. The first is that it may spend some
> time recovering orphaned files; this is much faster that a full fsck
> but it's still seconds or minutes. The second is that the journal sync
> may have failed in which case fsck terminates with "UNEXPECTED
> INCONSISTENCY" which requires a full fsck. This is similar to SU. In
> either case you only need a full fsck when things haven't worked out in
> line with the theory.
>> Is
>> it the same with su+j? If it does then I'll drop gjournal (and the
>> performance hit) and I'll use su+j when I jump to 9.0.
> The  SU equivalent of the journal sync is done before the crash
> happens. With SU you can have an instantaneous foreground fsck by
> deferring the recovery of lost files until the background check that
> runs after bootup. Journalling SU eliminates the few minutes
> of sluggish disk IO that that can cause.
> I've been disappointed by gjournal, the performance hit isn't as bad as
> background fsck but it is substantial and permanent, rather than a few
> minutes hare and there. I was hoping that gjournal would be more robust,
> but I've seen the occassional "UNEXPECTED INCONSISTENCY" just like I
> have with SU.
This is going to sound odd, I know, but what does your fstab look like 
with gjournal? I've only done /var and /usr like this:

/dev/ad4s1e.journal     /usr            ufs     rw,async        2       2

The only message that comes up for me after a crash is "consistent" or 
"clean". No wait, no fsck. The performance isn't exactly lightning 
though... :)

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