topic Re: NFS shows modified revision date on directory in Operating System - OpenVMS

NFS shows modified revision date on directory

Wim Van den Wyngaert — Mon, 09 Feb 2009 12:44:10 GMT

VMS 7.3 with TCP 5.3 eco 2.

I have node N1 with directory D1.
It is served via NFS to node N2.

When I do a dir/fu of D1 on N1 (so, not via NFS) it shows revision date somewhere 2007. Which is exact.

When I do a dir/fu on N2 (via NFS) it shows a date of maximum 15 secs ago.

If I do a dir on N2 every second, I see that the revision date changes every 15 seconds.

When I don't do anything on either node, the NFS server process does nothing (so, it's not changing the revision date).

Why ???

Wim

Re: NFS shows modified revision date on directory

Ian Miller. — Mon, 09 Feb 2009 15:00:03 GMT

ODS2 or ODS5 disk?

Re: NFS shows modified revision date on directory

Hoff — Mon, 09 Feb 2009 21:01:56 GMT

There are ECOs that fix revision and various other date-related weirdness in this OpenVMS version range.

See "Revision date moves backwards" and such in:

DEC-AXPVMS-VMS731_F11X-V0300--4.PCSI

I didn't specifically check for V7.3, but I'd expect the same issue there.

Re: NFS shows modified revision date on directory

Wim Van den Wyngaert — Tue, 10 Feb 2009 12:17:28 GMT

My reply to Ian duidn't make it. It's ODS2.

http://ftp.uma.es/Vms/parches/v7.3/VMS73_F11X-V0200.txt exists but I doubt that this is the reason. The description doesn't match (as most of the time it's vague).

Wim

Re: NFS shows modified revision date on directory

M. T. Hollinger — Tue, 10 Feb 2009 20:40:57 GMT

In the UNIX-inspired world of NFS, the modification time of a directory is updated whenever something in that directory changes, such as the creation of a new file. NFS clients sometimes use the modification time of the directory to validate their cache. A particular client might read a directory and then not bother to read it again until the modification time changes.

On OpenVMS, the modification date of an ODS-2 directory does not get updated every time a file is created or removed. That can lead to an unfortunate scenario. Someone creates a new file, but an NFS client can't see it because the client still has an old view of the directory and won't reload because of the timestamp.

The solution is for the NFS server to report the current time, or close to it, as the directory modification time. That way, NFS clients will realize they need to reread the directory, and they will be able to see newly-created files. As you noticed, it also means the directory will be unnecessarily re-read sometimes, but that's the price to be paid for correct behavior.

- Mark

Re: NFS shows modified revision date on directory

Wim Van den Wyngaert — Wed, 11 Feb 2009 11:43:40 GMT

I suspected this MArk. Supose I need more accuracy than 15 seconds. Can I modify the value of "15" ?

Wim