Faster Galera SST times using [sst] options.

This is a followup post to the article where I outlined how to use the power of linux pipes and pigz to compress and decompress your data in parallel for faster streaming backups.

Out of the box, the SST scripts used by Galera don’t try to optimize for speed. They are just trying to robust and not fail at the job they are required to do. That job is to get a Galera node back in sync with the cluster. But we can do better…

So I looked into the options you can pass to the SST process via adding [sst] to your .cnf file. I tested them in a lab, running the same OS and same DB version as the production database we were supported. This was to make sure the SST wouldn’t break.
And the results? we got a similar speed up in the SST duration that I had seen when we had been streaming backups to build a backup replica.

The time difference when dealing with large datasets is huge.

Notes:

  • Options added a .cnf file on every db server in the Galera cluster.
  • pigz needs to be installed on all db servers in the Galera cluster.
  • WARNING: Test this is a lab environment before rolling this out to production.
  • WARNING: Test this is a lab environment before rolling this out to production.
  • WARNING: Test this is a lab environment before rolling this out to production.
  • getting the idea yet… just test it first already.
  • These options will work with either:
    wsrep_sst_method=mariabackup
    or
    wsrep_sst_method=xtrabackup-v2

SST options to speed up using pigz and parallel threads:

[sst]
compressor='pigz -p 8'
decompressor='pigz -dc -p 8'
inno-backup-opts="--parallel=8"

Explanation:

compressor=’pigz -p 8′ : compress the streaming backup using pigz using 8 CPUs
decompressor=’pigz -dc -p 8′: decompress the streaming backup using pigz using 8 CPUs
inno-backup-opts=”–parallel=8″: backup the db using 8 parallel threads

 Documentation:

https://mariadb.com/kb/en/mariabackup-options/#-parallel
https://www.percona.com/doc/percona-xtrabackup/2.3/innobackupex/innobackupex_option_reference.html

Until next time.

Faster streaming backups using mariabackup and pigz

Are you looking for a faster way to stream a backup from one db server to another?

Maybe you are rebuilding a replica from the master after someone wrote to the slave and now the data is out of sync.

I had a look at what was out there in terms of articles about streaming backups.

Most of them got part of the way but clearly haven’t had people asking in chat “are we there yet?” over and over, wondering when their replicas will be back so they can direct the read traffic at them.
The key here is to use the parallel options that come with mariabackup and use pigz to compress and decompress in parallel.

Do you want speed?
Do you want to saturate the 10Gigabit bonded link or InfiniBand (I wish…) ?
Do you have spare CPUs to use?

WARNING:

  • This command assumes the destination directory is empty.¬†
  • The command will 8 CPUs (4 for mariabackup and 4 for pigz) on the source
  • The command can use up to 8 CPUs (4 for pigz to decompress, 4 for mbstream)
  • Don’t run pigz without -p option. As by default it will use all CPUs available.

The command:

mariabackup --backup --slave-info --tmpdir=/tmp --stream=xbstream --parallel=4 --datadir=/var/lib/mysql 2>backup.log | pigz -p 4 | ssh -q replica -t "pigz -dc -p 4 | mbstream --directory=/var/lib/mysql -x --parallel=4"

Explanation of the command:

  1. This command will take a streaming backup (using xbstream) in parallel from the database in /var/lib/mysql.
  2. It will write output the backup.log (just in case you need to debug…)
  3. Then it will pipe that toq pigz (parellel gzip) which will compress in parallel.
  4. This stream of compressed xbstream will be sent encrypted via ssh to host called replica.
  5. On the replica, the compressed xbstream will be uncompressed by pigz, then piped thru mbstream into the /var/lib/mysql directory.

Next steps:

  1. Prepare the backup using the appropriate amount of RAM.
    mariabackup --prepare --use-memory=16G --target-dir=/var/lib/mysql/
  2. Change the ownership of the destination datadir
    chown -R mysql:mysql /var/lib/mysql
  3. Start the db
    systemctl start mariadb
  4. Look at xtrabackup_slave_info to get the slave info
    cat /var/lib/mysql/xtrabackup_slave_info
  5. Change the master using CHANGE MASTER using that info.

Until next time.