Re: [EXT] link files not being created

[Stefan Solbrig <stefan.solbrig@xxxxx>]

Hi Xavi,

On Mon, Oct 17, 2022 at 1:03 PM Stefan Solbrig <stefan.solbrig@xxxxx> wrote:

Dear all,

I was doing some testing regarding to GlusterFS link files (as they are created by a "move" operation). According to this document: https://www.gluster.org/glusterfs-algorithms-distribution/  If a link file is missing, it should be created after accessing the file.
However, I don't see this behaviour.  If I delete (by hand) a link file on the brick, the file is still accessible, but the link file is never recreated. I can do an "open" or a "stat" on the file without getting an error, but the link file is not created.
Is this the intended behaviour? Or am I misunderstanding the above mentioned document?

You shouldn't access or modify the backend filesystems manually, you can accidentally create unexpected problems if you don't fully understand what you are doing.

That said, most probably the access to the file is still working because Gluster is using its cached information to locate the file. If the client mount is restarted, probably the file won't be accessible anymore unless you disable the "lookup-optimize" option (and this should recreate the link file).

Regards,

Xavi

Thanks for the quick reply!  Maybe I should explain better my motivation for the above mentioned experiments. I have a large production system running GlusterFS with almost 5 PB of data (in approx 100G of inodes). It's a distributed-only system (no sharding, not dispersed).  In this system, the users sometimes experience the problem that they cannot delete a seemingly empty directory.  The cause of this problem is, that the directory contains leftover link files, i.e. dht link files where the target is gone. I haven't identified yet why this happens and I don't have a method to provoke this error (otherwise I would have mentioned it on this list already.)  But my quick & dirty fix is, to delete these leftover link files by hand.  (These leftover link files are not being cleaned up by a "rebalance".) 

The reason for my experiments with link files is: what happens if for some reason I accidentally delete a link file where the target still exists?

In the experiments (not on the production system) I also tried umounting and remounting the system, and I already tried setting "loopup-optmize = off". It doesn't affect the outcome of the experiments.

best wishes,

Stefan

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