Really odd FTP issue

[NickFitz]

No, nothing special around row 50 - we've tried with other file sizes and it is just overwriting the new data as far as it needs to in the file.

It sounds like the destination file is being opened for writing, but never closed. That would leave it hanging and presumably the OS would eventually close the open file handle but without any awareness of what had been done to it. This could, in theory, leave the content on disk having been overwritten but the file descriptor not having been told the new length of the file. Then the file would have the new content at the start but have the same length as the old file from the point of view of whatever reads it.

The people that the data is going to have now discovered that the new file has its original header and the new header as well.

This also makes it sound like the file modification is happening but being left hanging. But by this point, I'd be demanding hex dumps of individual disk sectors so I could see what was really going on

I wonder if we can send a Delete before we send the next file, or maybe move/rename the previous file when we send the new one.

That might work but if it's what I suggest, then fixing the sending FTP client to properly close the file (or the receiving one to do so if it's their fault) would resolve the issue by making things work properly, which is better than a clumsy and haphazard "fix" that seems to work and does… for now

[woody1]

It sounds like the destination file is being opened for writing, but never closed. That would leave it hanging and presumably the OS would eventually close the open file handle but without any awareness of what had been done to it. This could, in theory, leave the content on disk having been overwritten but the file descriptor not having been told the new length of the file. Then the file would have the new content at the start but have the same length as the old file from the point of view of whatever reads it.

I've never seen UNIX doing anything like this but I guess you never know.

As an experiment, I would try the same FTP transfers (small text file overwriting large text file) from the UNIX server to itself (ie. using the UNIX FTP client). This would take the Windows side of things out of the equation altogether.