mylvmbackup

JFYI, I now placed a PDF of my MySQL Conference talk slides about "Performing MySQL backups using Linux LVM Snapshots" on my MySQL talks page. Enjoy!

While reading Colin's post about LugRadio Live, I stumbled over the Zumastor Linux Storage Project. Going through the project home page and their HOWTO got me curious - could this eventually become an alternative to using DRBD (for replicating data) and LVM snapshots (for performing backups)?

Zumastor is Free software that adds enterprise storage features (primarily improved snapshots and remote replication) to Linux.

Snapshots

LVM already lets administrators create snapshots, but its design has the surprising property that every block you change on the original volume consumes one block for each snapshot. The resulting speed and space penalty usually makes the use of more than one or two snapshots at a time impractical.

Zumastor keeps all snapshots for a particular volume in a common snapshot store, and shares blocks the way one would expect. Thus making a change to one block of a file in the original volume only uses one block in the snapshot store no matter how many snapshots you have.

Replication

Andrew Tridgell's rsync is a wonderful tool for replicating files remotely. However, when doing periodic replication of large numbers of infrequently changing files, the overhead for figuring out what files need to be sent can be extreme.

Zumastor keeps track of which block change between one snapshot and the next, and can easily send just the changed blocks. Thus Zumastor can do frequent replication of large filesystems much more efficiently than rsync can.

I assume it's not ready for production use yet, but it would sure be interesting to investigate on how to utilize it for the purpose of running MySQL on top of it...

I will keep an eye on this project, I wonder if I will have to add support for Zumastor snapshots to mylvmbackup at some point?

I am happy to announce the release of mylvmbackup version 0.8. mylvmbackup is a tool for quickly creating backups of a MySQL server's data files. To perform a backup, mylvmbackup obtains a read lock on all tables and flushes all server caches to disk, makes an LVM snapshot of the volume containing the MySQL data directory, and unlocks the tables again. The snapshot process takes only a small amount of time. When it is done, the server can continue normal operations, while the actual file backup proceeds.

Below is the list of changes since version 0.6. You may wonder what happened to version 0.7 - it had a rather short life cycle as I was informed about a bug that I fixed quickly before I made a wider release announcement of 0.7.

• Fixed a bug in the InnoDB recovery function: the second mysqld process clobbered the socket file of the primary MySQL instance (thanks to Alain Hoang for reporting this)
• Updated the man page, noted some other limitations of the InnoDB recovery function
• Bug fix: use the correct mysqld parameter to provide an alternative PID file (--pid-file instead of --pidfile) - thanks to Guillaume Boddaert and Jim Wilson for reporting this!
• Added option "--skip_mycnf" to skip including a copy of the MySQL configuration file in the backup, added a safety check that the file actually exists prior to backing it up.

Updated package are available from the home page and via the openSUSE Build Service as usual. Updated packages for Debian/Ubuntu and Gentoo Linux should also be available shortly. Enjoy!

Speaking of LVM snapshot backups: I will be giving a talk about this subject at our MySQL Conference 2008 in Santa Clara, CA next week. If you are curious about how MySQL can be backed up using this technology, please consider to stop by!