On Aug 22, 2006, at 2:07 PM, Manuel Bouyer wrote:
>> 1) How well does NetBSD >=3 support fsck of a
dirty FFS file
>> systems that were mounted with the
"softdep" option before the
>> event that
>> made them dirty?
>
> It doesn't support this at all. Does this exists in
FreeBSD yet ?
Since FreeBSD v5, yes:
http://www.mckusick.
com/softdep/
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handb
ook/
configtuning-disk.html#SOFT-UPDATES
Be cautious in that doing an fsck of very large filesystems
(in the
terabyte range) can require a lot of resources for fsck to
run,
whether in the background or foreground, and the system will
be under
a lot of I/O load until that bgfsck completes.
>> 2) How well does NetBSD >=3 support the snapshot
functionality? I
>> see
>> that there's a kernel option to enable it. Is it
considered
>> stable and
>> reliable? What opinion do people who have used it
have of it?
>
> I'm using it (without softdeps) and didn't encounter
major problems
> with it yet. It's used by dump -X in my case.
For the most part, filesystem snapshots have worked pretty
well under
a bunch of cases on FreeBSD; the example of using
dump/restore is a
good one, also for trying to obtain a more consistent
file-level
backup of an active database, and so forth.
However, snapshots are better thought of as the filesystem
equivalent
of using tags within a version control system like CVS or
SVN; they
let you refer to the entire contents of the filesystem as a
single
consistent entity frozen at one point in time. They are not
a
substitute for keeping real backups on other storage...
Note that there have also been some deadlock issues with
softdeps and
snapshots under FreeBSD (at least), which have generally
been
triggered by extremely low diskspace conditions-- for
example, doing
an installworld where the boot partition is very low on
space.
--
-Chuck
|