MySQL Cluster Overview
MySQL Cluster
is a technology that enables
clustering of in-memory databases in a shared-nothing system. The
shared-nothing architecture allows the system to work with very
inexpensive hardware, and with a minimum of specific requirements
for hardware or software.
MySQL Cluster is designed not to have any single point of failure.
In a shared-nothing system, each component is expected to have its
own memory and disk, and the use of shared storage mechanisms such
as network shares, network file systems, and SANs is not recommended
or supported.
MySQL Cluster integrates the standard MySQL server with an in-memory
clustered storage engine called NDB
(which stands for “N
etwork
D
ataB
ase
”). In our
documentation, the term NDB
refers to
the part of the setup that is specific to the storage engine,
whereas “MySQL Cluster
” refers to the combination of
one or more MySQL servers with the NDB
storage engine.
A MySQL Cluster consists of a set of computers, known as
hosts
, each running one or more processes.
These processes, known as nodes
, may include
MySQL servers (for access to NDB data), data nodes (for storage of
the data), one or more management servers, and possibly other
specialized data access programs. The relationship of these
components in a MySQL Cluster is shown here:
All these programs work together to form a MySQL Cluster (see
Chapter 4, MySQL Cluster Programs
. When data is stored by the
NDB
storage engine, the tables (and
table data) are stored in the data nodes. Such tables are directly
accessible from all other MySQL servers in the cluster. Thus, in a
payroll application storing data in a cluster, if one application
updates the salary of an employee, all other MySQL servers that
query this data can see this change immediately.
The d
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