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Issue with MariaDB backup using LVM snapshot

 

Hello.

We are using a backup procedure based on a combination of LVM snapshots and rsync.

In particular, the procedure is the following:



> ...
> mysql -h -u -p -e "FLUSH TABLES WITH READ LOCK; \! lvcreate -L -s -n "
> 
> mount
> 
> ...
> 
> rsync .......

At the end, we change the working directory, unmount  and lvremove .

Sometimes, randomly, the umount command works but the lvremove fails and we are left with the lvm snapshot unmounted but we are unable to remove it.

We tried to force a removal without success with the following error:



> Logical volume contains a filesystem in use

We didn't find any process using that device using lsof and we can't find any handler keeping the device busy.

Even a mariadb restart doesn't fix it and the only solution is to reboot the server.

The only thing we noticed is a message upon the snapshot creation:



> File descriptor 4 (socket:[201844800]) leaked on lvcreate invocation. Parent PID 1564033: mysql

We know that this is the mysql unix socket.



Have you ever had such an issue?



Thanks a lot.

Kind regards.



Riccardo