ext2 filesystem lockups

[Astrodog]

On Fri, 25 Feb 2005 04:20:15 +1100 (EST), Bruce Evans <bde at zeta.org.au> wrote:
> On Wed, 23 Feb 2005, Astrodog wrote:
> 
> > On Thu, 24 Feb 2005 01:06:54 +0100, Markus Trippelsdorf
> > <markus at trippelsdorf.de> wrote:
> > > On Wed, 2005-02-23 at 19:35 -0300, João Carlos Mendes Luís wrote:
> > > > David O'Brien wrote:
> > > > > On Wed, Feb 23, 2005 at 04:29:19PM +0100, Markus Trippelsdorf wrote:
> > > > >>Which filesystem is recommended for multi-OS file exchange?
> > > > >
> > > > > I've heard enought reports of ext2 problems on 32-bit i386, that I don't
> > > > > trust it in situations that "have to work".  By far the most widely
> 
> I use it with no problems and trust it is easy to fix if some turn up.
> I haven't tried it on amd64.
> 
> > > > > supported FS is vfat32 [mount_msdosfs(8)].
> > > >
> > > > The last time I had to use msdosfs, on 4.* it was extremely slow
> > > > compared to UFS on the same disk.  Did this get better on 5.*?
> 
> The main slownesses in msdosfs are pessimal (random) block allocation
> for the first block in a file, and non-use of some important system
> features (clustering and VMIO).  This has not been fixed in 5.x AFAIK.
> 
> > > I want to use the filesystem for my music collection, so I'm willing to
> > > trade fastness for reliability.
> 
> ffs is the most reliable of the read-write file systems in FreeBSD.
> cd9660 is probably more reliable, and it is most portable, but it is
> less convenient since it is read-only in the kernel.  If you only need
> to write under one OS then it is fairly safe to use ffs for writing
> under FreeBSD and ext2fs for writing under Linux.
> 
> > vfat32/MSDOSFS is going to be the most supported, seeing as I can
> > mount these types of filesystems on just about every OS out there.
> > Regarding speed, there's a pretty big tradeoff, but even if it reduces
> > drive I/O by %50, you're still above the speed of a 10/100 NIC, and
> 
> A big reduction is 99% :-).  Reductions of 90% are common for small
> files.
> 
> > certainly above the speed an MP3 streams at. (You're right at the
> > limit, for DVD Video) In short, yes, it will be slower, but for the
> > purposes of storing MP3s, and whatnot, the speed tradeoff is
> > inconsequencial(sp), and it beats loosing everything every once in
> > awhile.
> 
> But msdosfs is fundamentally very unreliable.  Corrupted FATs give more
> global problems than corrupted inodes.  It doesn't help that the msdosfs
> implementation cheats with FAT updates and does them fully asynchronously
> (delayed up to 30+ seconds) using delayed writes unless you mount with
> "-o sync" (which gives sync data too, and thus extreme slowness).  So
> msdosfs by default is closer to ffs with "-o async" and thus more
> unreliable then necessary.
> 
> Bruce
> 

I suppose the real lesson here, is why would you want to use anything
that doesn't support UFS? ;)