Oracle 5.0, Справочное руководство

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MySQL 5.0 FAQ: MySQL Cluster
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for hash indexes by using the
MAX_ROWS
option for
CREATE TABLE
. In general, setting
MAX_ROWS
to
twice the number of rows that you expect to store in the table should be sufficient.
For similar reasons, you can also sometimes encounter problems with data node restarts on nodes
that are heavily loaded with data. In MySQL Cluster NDB 7.1 and MySQL Cluster NDB 7.2, the
addition of the
MinFreePct
parameter helps with this issue by reserving a portion (5% by default)
of
DataMemory
[1559] and
IndexMemory
[1560] for use in restarts. This reserved memory is not
available for storing
NDB
tables or data.
B.10.14: MySQL Cluster uses TCP/IP. Does this mean that I can run it over the Internet, with
one or more nodes in remote locations?
It is very unlikely that a cluster would perform reliably under such conditions, as MySQL Cluster was
designed and implemented with the assumption that it would be run under conditions guaranteeing
dedicated high-speed connectivity such as that found in a LAN setting using 100 Mbps or gigabit
Ethernet—preferably the latter. We neither test nor warrant its performance using anything slower than
this.
Also, it is extremely important to keep in mind that communications between the nodes in a MySQL
Cluster are not secure; they are neither encrypted nor safeguarded by any other protective mechanism.
The most secure configuration for a cluster is in a private network behind a firewall, with no direct
access to any Cluster data or management nodes from outside. (For SQL nodes, you should take the
same precautions as you would with any other instance of the MySQL server.) For more information,
see
Section 17.5.10, “MySQL Cluster Security Issues” .
B.10.15: Do I have to learn a new programming or query language to use MySQL Cluster?
No. Although some specialized commands are used to manage and configure the cluster itself, only
standard (My)SQL statements are required for the following operations:
• Creating, altering, and dropping tables
• Inserting, updating, and deleting table data
• Creating, changing, and dropping primary and unique indexes
Some specialized configuration parameters and files are required to set up a MySQL Cluster—see
Section 17.3.2, “MySQL Cluster Configuration Files” , for information about these.
A few simple commands are used in the MySQL Cluster management client (
ndb_mgm
) for tasks
such as starting and stopping cluster nodes. See Section 17.5.2, “Commands in the MySQL Cluster
Management Client” .
B.10.16: How do I find out what an error or warning message means when using MySQL
Cluster?
There are two ways in which this can be done:
• From within the
mysql
client, use
SHOW ERRORS
or
SHOW WARNINGS
immediately upon being
notified of the error or warning condition.
• From a system shell prompt, use
perror --ndb error_code
.
B.10.17: Is MySQL Cluster transaction-safe? What isolation levels are supported?
Yes. For tables created with the
NDB
storage engine, transactions are supported. Currently, MySQL
Cluster supports only the
READ COMMITTED
[1121] transaction isolation level.
B.10.18: What storage engines are supported by MySQL Cluster?
Clustering with MySQL is supported only by the
NDB
storage engine. That is, in order for a table to
be shared between nodes in a MySQL Cluster, the table must be created using
ENGINE=NDB
(or the
equivalent option
ENGINE=NDBCLUSTER
).