> Another important change is that it is no longer necessary to run
> tunefs in single user mode to activate soft updates. All that is
> needed is to add the "softdep" mount option to the partitions you
> want soft updates enabled on in /etc/fstab."
> I especially like not having to run tunefs :-)

Having the softdep option in fstab(5) doesn't gel well with the 
recent background-fsck work being introduced by Kirk - although it 
works from what I can tell.

In both OpenBSD and NetBSD, a filesystem mounted with the ``softdep'' 
option will update the super-block flags with the FS_DOSOFTDEP bit, so 
it's easy for fsck(8) to tell how an unclean filesystem was last 
mounted.  In fact, OpenBSD has ``if 0''d code that allows unclean 
filesystem mounts if they have that FS_DOSOFTDEP bit set (NetBSD 
doesn't seem to have this).

The problem I think is where a ``mount -u'' is done to downgrade a 
filesystem from soft-udpates to no soft-updates.  Both OpenBSD and 
NetBSD have comments to the effect

                 * Flush soft dependencies if disabling it via an update
                 * mount. This may leave some items to be processed,
                 * so don't do this yet XXX.

and both ignore the problem (leaving soft-updates set).  I don't 
think there's a satisfactory way of doing this - in much the same way 
as downgrading a read-write filesystem to read-only doesn't quite 
work.  If certain operations are in effect (like a background fsck in 
the first instance or a reference is held to a file with a zero link 
count in the second), all hell can break loose.

Having said all that, I quite like the softdep option in OpenBSD & 
NetBSD, despite it only being a half-option :-)

>                          The second improvement, contributed by
> [EMAIL PROTECTED], is a new directory allocation policy (codenamed
> "dirpref"). Coupled with soft updates, the new dirpref code offers up
> to a 60x speed increase in gluk's tests, documented here:" 

I do like the dirpref stuff, but I can't comment much on it 
except that it looks like a good change that should be fairly easy to 
bring into FreeBSD.

I'm not 100% convinced about the algorithm to avoid clusters filling 
up with directory-only entries (it looks like a worst-case would fill 
a cluster with 50% directories and 50% files leaving a bad layout when 
the directories are populated further), but then the non-dirpref 
scheme has some far worse worst-case scenarios ;-)
Brian <[EMAIL PROTECTED]>                        <brian@[uk.]FreeBSD.org>
      <http://www.Awfulhak.org>                   <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !

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