scp and SGI DMF

[Iain Morgan]

Hello,

For some time now, our users have been encountering a problem when using scp
to overwrite files on our mass-storage system, which uses SGI's DMF
product. I don't have any data as to whether or not any other HSMs would be
similarly affected.

The scenario is that a user is overwriting a file (via scp) that has previously
been migrated to tape. The scp opens the file for writing, but does not
truncate the file. This causes DMF (the HSM) to recall the file from tape and
the scp hangs until it is successfully recalled.

Unfortunately, these recalls can take several hours depending on how active the
tape drives are.

So, I'm wondering if there would be any interest in either adding (yet another)
command-line option to add O_TRUNC to the open() flags when writing a file or
perhaps to change the default behaviour. (I'm assuming the latter is unlikely.)

I should note that sftp doesn't seem to have the same problem. However, the lack
of a recursive copy makes it problematic for many of our users.

Thanks

--
Iain Morgan