[Lustre-discuss] MDS files attribute

[Dilger, Andreas]

On Nov 29, 2012, at 12:39 AM, Alfonso Pardo wrote:
> I need to monitoring a directory in the lustre file system.

We don't have any inotify or dnotify support for Lustre.  In Lustre 2.x it is possible to monitor the whole filesystem with the Lustre ChangeLog functionality.  It might be an interesting project for someone to wire up the ChangeLog to the kernel inotify/dnotify, though that would obviously take some significant effort.

> I want to change the group id for each new file written in the directory.

You could just use the BSD-style directory group ownership to force all new files created there to have a specific group ID?

    chgrp {group} /path/to/dir
    chmod g+s /path/to/dir

Now all new files will have the group "{group}".  This is not Lustre-specific, it works for other filesystems as well.

> Is it possible to ask to the MDS the file attributes to obtain more speed in my chown script?

The "lfs find" code does fetch attributes from just the MDS.  There was a proposal for a new Linux syscall to be able to get specific attributes of a file instead of all of them:

http://lists.openwall.net/linux-ext4/2010/07/01/11

but it never quite made it into the kernel.

> One more thing, is it possible to ask to the MDS the last wrote files? And then apply the new group id only to the new files.
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> Thanks in advance
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Cheers, Andreas
--
Andreas Dilger
Lustre Software Architect
Intel Corporation