Re: Lost file-system story

[Matthew Mondor <mm_lists%pulsar-zone.net@localhost>]

On Fri, 9 Dec 2011 22:12:25 -0500
Donald Allen <donaldcallen%gmail.com@localhost> wrote:

> Linux systems do periodically write ext2 meta-data to the disk. And
> ext2 fsck has always been very good, and has gotten better over the
> years, due to the efforts of Ted T'so. I first installed Linux in
> 1993, almost 20 years ago, and have been using it continuously ever
> since. I have *never* lost an ext2 filesystem and I've never mounted
> one sync.

I'm not sure if it's the case on Linux with ext2, but by default NetBSD
FFS mounts are not sync, nor async; metadata is sync and data blocks
are async.  In async mode, all data is asyncronously written, including
the metadata, and in sync mode everything is written synchronously (the
default OpenBSD uses, if I recall).  I just wanted to specify this as
you mentioned not mounting your ext2 systems in sync mode, but a
default NetBSD FFS mount will not be in sync mode either.

Other available options with FFS are using soft dependencies (softdep)
or WAPBL metadata journalling (log), with which it is possible to have
increased performance VS the default mode, without really sacrificing
reliability, unlike with the fully async mode.  In those modes,
metadata is written asynchroneously as well.

Sorry if what I said is already obvious to you,
-- 
Matt