MySQL 5.0 FAQ: MySQL Cluster
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no single node group has all its nodes alive, in which case network partitioning (the “split-brain”
scenario) becomes possible. Then an arbitrator is required. All cluster nodes recognize the same
node as the arbitrator, which is normally the management server; however, it is possible to configure
any of the MySQL Servers in the cluster to act as the arbitrator instead. The arbitrator accepts the
first set of cluster nodes to contact it, and tells the remaining set to shut down. Arbitrator selection is
controlled by the
ArbitrationRank
configuration parameter for MySQL Server and management
server nodes. For more information about this parameter, see
Section 17.3.2.4, “Defining a MySQL
Cluster Management Server”
.
The role of arbitrator does not in and of itself impose any heavy demands upon the host so designated,
and thus the arbitrator host does not need to be particularly fast or to have extra memory especially for
this purpose.
B.10.27: What data types are supported by MySQL Cluster?
In MySQL 5.0;, MySQL Cluster supports all of the usual MySQL data types, including (beginning with
MySQL 5.0.16) those associated with MySQL's spatial extensions; however, the
NDB
storage engine
does not support spatial indexes. (Spatial indexes are supported only by
MyISAM
; see
Section 12.16,
“Spatial Extensions”
, for more information.) In addition, there are some differences with regard to
indexes when used with
NDB
tables.
Note
In MySQL 5.0, MySQL Cluster tables (that is, tables created with
ENGINE=NDB
or
ENGINE=NDBCLUSTER
) have only fixed-width rows. This means that (for
example) each record containing a
VARCHAR(255)
column will require space
for 255 characters (as required for the character set and collation being used
for the table), regardless of the actual number of characters stored therein. This
issue is fixed in MySQL 5.1 and later; however, we do not plan to backport this
functionality to MySQL 5.0.
See
Section 17.1.5, “Known Limitations of MySQL Cluster”
, for more information about these issues.
B.10.28: How do I start and stop MySQL Cluster?
It is necessary to start each node in the cluster separately, in the following order:
1. Start the management node, using the
ndb_mgmd
command.
You must include the
-f
[1624]
or
--config-file
[1624]
option to tell the management node
where its configuration file can be found.
2. Start each data node with the
ndbd
command.
Each data node must be started with the
-c
[1651]
or
--ndb-connectstring
[1651]
option so
that the data node knows how to connect to the management server.
3. Start each MySQL Server (SQL node) using your preferred startup script, such as
mysqld_safe
.
Each MySQL Server must be started with the
--ndbcluster
[1610]
and
--ndb-
connectstring
[1610]
options. These options cause mysqld to enable
NDBCLUSTER
storage
engine support and how to connect to the management server.
Each of these commands must be run from a system shell on the machine housing the affected node.
(You do not have to be physically present at the machine—a remote login shell can be used for this
purpose.) You can verify that the cluster is running by starting the
NDB
management client
ndb_mgm
on
the machine housing the management node and issuing the
SHOW
or
ALL STATUS
command.
To shut down a running cluster, issue the command
SHUTDOWN
in the management client. Alternatively,
you may enter the following command in a system shell:
shell>
ndb_mgm -e "SHUTDOWN"
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