Tag Archive for Cluster 7.0

MySQL Cluster Data Node restart times

Restart times have been reduced in MySQL Cluster 6.3.28a & 7.0.9a – refer to that article for the new timings: http://www.clusterdb.com/mysql-cluster/mysql-cluster-restarts-get-faster/

Restarts are required for certain, infrequent maintenance activities. Note that there is no loss of service while a single node restarts.

When a data node restarts, it first attempts to load the data into memory from the local log files and then it will catch up with any subsequent changes by retrieveing them from the surviving node(s) in its node group.

 Based on this, you would expect the time taken to restart a data node to be influenced by:

  1. The amount of data that was stored on the data node before the restart
  2. Rate of updates being made to the data during the restart
  3. Network performance (assuming the data is being updated during recovery)

The times will also be influenced bycertain configuration parameters, performance of the host machine and whether the multi-threaded data node (ndbmtd) is being used.

To provide some insight into how these factors impact restart times, tests have been performed where the following factors are varied:

  • Database size (Each Gbyte is made up of 1,000,000 tuples in each of 5 tables)
  • Whether traffic is running or not (a single thread using the NDB API to send in up to 2K tps (10K updates/second))
  • Whether the 2 data nodes in the node group are on the same host or separated by a Gbit Ethernet network

The following factors are kept constant:

  • Physical hosts: Intel Core 2 Quad Q8200@2.33 GHz; 7.7 GBytes RAM
  • NoOfFragmentLogFiles: 300
  • MaxNoOfExecutionThreads=4

Here are the observed results:

Data Node restart times

Data Node restart times

There are a couple of things to note from these results:

  • Using the multi-threaded data node (ndbmtd) greatly improves the restart time (in this case, 4 threads were available, improvements could be even greater on an 8 core/thread system)
  • Results become less predictable when heavy update traffic is being processed (in this case, up to 10,000 updated rows/second on a single node group). In the tests, no attempt was made to regulate this traffic and the test application was run on the same host as the one of the data nodes. Changes to the rate of updates will vary how long it takes for the restarting node to catch-up as it’s a moving target.

There is another recovery/restart scenario. The measurements shown above assumed that the file system on the data node’s host was intact and could be used to recover the in-memory copy – if that were not the case (or the data nodes were restarted with the “initial” option) then all of the data would have to be recovered from the surviving data node(s) in the same node group. As a comparison restarting a 6 Gbyte data node with the “initial” option took 20 minutes compared to 8 minutes without it (ndbmtd, over Gbit n/w).

New MySQL Cluster maintenance release: 7.0.6

MySQL Cluster version 7.0.6 has been released. MySQL Cluster 7.0.6 is available in source and binary form for a number of platforms from our download pages.

The release in source form can in addition be downloaded from the MySQL FTP server.

MySQL Cluster version 7.0.6 is using MySQL Server version 5.1.34 and contains all bug fixes and changes that MySQL Server 5.1.33 and 5.1.34 contain.
Following changes were made in MySQL Cluster 7.0.6 since the previous release 7.0.5:

Functionality added or changed:

  • Important Note: It is possible in MySQL Cluster NDB 7.0.6 and later   to perform online upgrades from MySQL Cluster NDB 6.3.8 and later MySQL   Cluster NDB 6.3 releases, or from MySQL Cluster NDB 7.0.5 or later MySQL Cluster NDB 7.0 releases.
  • It was not possible to perform an online upgrade from any MySQL Cluster  NDB 6.x release to MySQL Cluster NDB 7.0.5 or any to earlier MySQL Cluster NDB 7.0 release. (Bug#44294)
  • The ndb_config utility program can now provide an offline dump of all MySQL Cluster configuration parameters including information such as default and permitted values, brief description, and applicable section of the config.ini file.

The documentation has been updated accordingly and a full change log will be found.

For more information about changes and bugs fixed in MySQL Server 5.1.33 and 5.1.34 please refer to the reference manual.