file-copy corruption

[Albert Graham]

Hi Terry,

I tend to disagree with the other who have replied so far, I've found 
NFS to be 100% reliable for many years, with large clusters of clients 
using many flavors of Unix, Whenever things have failed I've always 
being able to find the root cause.

I'd suggest that you look are your messages file for indications of the 
problem. Also one tool you can .use is nfsstat (man nfsstat) it should 
indicate NFS related bad calls.

On any recent Linux, it would be very rare for there to be "no 
indication", so your log files are your friend.

If you really cannot find any message or indication, it stands to reason 
that the files in question may have been open/updated by another user or 
process during the gzip process, is that possible ?

I would agree that Rsync is a good choice for this task (you could run 
"rsync --dry-run --stats" to show any differences) that exist.

Albert.

T. Horsnell wrote:
> I'm in the process of moving stuff from our Alpha fileserver
> onto A linux replacement. I've been using gnu-tar to copy filesystems
> from the Alpha to to the Linux NFS-exported disks over a 1Gbit LAN,
> followed by diff -r to check that they have copied correctly (I wish
> diff had an option to not follow symlinks..). I've so far transferred
> about 3 TiB of data (spread over several weeks) and am concerned
> that during this process, 3 files were mis-copied without any
> apparent hardware-errors being flagged. There was nothing unusual
> about these files, and re-copying them (with cp) fixed the problem.
>
> Are occasional undetected errors like this to be expected?
> I thought there were sufficient stages of checksumming/parity 
> (both boxes have ECC memory) etc to render the probability
> of this to be vanishingly small.
>
> On all 3 files, multiple retries of the diff still resulted
> in a compare error, which was then fixed by a re-copy. This
> suggests that the problem occurs during the 'gtar' phase, rather
> than the 'diff -r' phase.
>
> Does anyone know of a network-exercise utility I can use
> to check the LAN component of the data-path?
>
> Cheers,
> Terry.
>
>