#DBHangOps 08/21/14 -- GTIDs, Shared Storage, and more!

You can watch the recording below:

Hello everybody!

Join in #DBHangOps this Thursday, August, 21, 2014 at 11:00am pacific (18:00 GMT), to participate in the discussion about:

• GTIDs in MariaDB Demo from Gerry!
• Shared storage and MySQL
  • How about NFS?
• Index Fragmentation (requested by Shlomi)

Be sure to check out the #DBHangOps twitter search, the @DBHangOps twitter feed, or this blog post to get a link for the google hangout on Thursday!

See all of you on Thursday!

Show notes

GTIDs in MariaDB

• MariaDB is always implicitly running with GTIDs under the hood, even if you don't have them enabled.
  • This allows you to easily enable/disable GTIDs on a running server without shutting down a whole topology of machines
  • You can convert a master's binlog coordinates to GTID coordinates using "SELECT BINLOG_GTID_POS('binlog_file.000001', binlog_pos)"
    • This is similar to doing "MASTER_AUTO_POSITION" in Oracle MySQL.
• Future version of MySQL 5.7 will begin allowing for enabling GTIDs without restarting MySQL
• MySQL creates a UUID to identify itself for GTIDs whereas MariaDB depends on the setting of server_id
  • If you want stronger uniqueness for server_id, you can use the "inet_aton()" function in MySQL to create a numerical representation of an IP address

Shared storage and NFS

• A lot of the historical issues with NFS have improved with NFSv4 since there is now mandatory and advisory locking support
• The "binlog_impossible_mode" variable is extremely useful to set for MySQL servers running on NFS
  • http://dev.mysql.com/doc/refman/5.6/en/replication-options-binary-log.html#sysvar_binlog_impossible_mode
  • Allows you to dictate how mysql should behave if it can't write it's binlogs
• A word of caution: historically, periodic performance issues with a database server could be as a result of shared storage if it's used by other machines
• Also be cognizant of NFS issues and documentation with mysql -- http://bugs.mysql.com/bug.php?id=71969
• Would shared storage be better going forward now that we can start using SSDs in shared storage devices?
• Ideally, putting less-performance-critical data onto NFS would allow you to leverage the best of both worlds
  • There's an option to store individual tables on different data directories in future versions of MySQL?