ufs write safety

[David Kewley]

On Wednesday 25 May 2005 15:45, Dave Jones wrote:
> On Wed, May 25, 2005 at 03:38:22PM -0700, David Kewley wrote:
>  > Can anyone here provide experience reports or pointers to reports,
>  > regarding the safety of Linux's write support for Sun UFS?  It is
>  > marked as experimental and dangerous, but it appears to have been
>  > around since 1998.  I'm wondering whether this might be one of
>  > those things that works fine but still carries old labels.
>
> It doesn't get any real attention upstream, so I've no particular
> belief that its gotten any more stable than it ever was (wrt writes).
> For this reason, the write support is disabled in Fedora.
>
>  > I have several external RAID arrays that up to now have been
>  > attached to Sun boxes and formatted with UFS filesystems.  I will
>  > be attaching these arrays now to a RHEL 4 host.
>
> UFS is also unavailable in RHEL4.
>
>  > If I can safely get away with it,  I'd prefer to keep writing to
>  > the UFS volumes since we're talking  about several TB of data.
>
> I certainly wouldn't trust it with data I wanted to keep.
>
>  > then I will need to transfer the data to a Linux filesystem with
>  > spare TB of space, reformat the external filesystems, and move the
>  > data back (or variations on that plan).  These are filesystems
>  > that several people use for daily work, so I'd rather avoid the
>  > copy time if possible.
>
> This is unfortunatly, probably the best way forward.

Thanks *very* much, Dave -- it's good to hear this from someone highly 
involved in the kernel.  I'll take your advice.

I am using UFS and XFS in RHEL4 by rebuilding the kernel with those 
filesystems enabled.  The filesystems appear to work fine; I know 
others are also using XFS in RHEL4.

I've just now for the first time mounted that Sun UFS volume with this 
kernel.  I was able to do the one thing I tried -- 'ls' the top-level 
directory. :)  I had enabled write support in the kernel and mounted it 
rw; I'm now going back & re-building that kernel without write support, 
per your advice.  I could mount ro, but that's not as safe as disabling 
writes.

I know that using these filesystems on RHEL4 is neither supported nor 
recommended by Red Hat.  As an academic site-license customer, however, 
I don't get RH support anyway, so I get to make my own choices 
appropriate to my risk tolerance. ;)

David