MySQL Cluster Programs
1618
• Range scan using ordered index
When an ordered index is used, it performs a scan in the same manner as the full table scan, except
that it scans only those records which are in the range used by the query transmitted by the MySQL
server (SQL node). All partitions are scanned in parallel when all bound index attributes include all
attributes in the partitioning key.
With benchmarks developed internally by MySQL for testing simple and batched primary and unique
key accesses, we have found that using SCI sockets improves performance by approximately 100%
over TCP/IP, except in rare instances when communication performance is not an issue. This can
occur when scan filters make up most of processing time or when very large batches of primary key
accesses are achieved. In that case, the CPU processing in the
ndbd
processes becomes a fairly large
part of the overhead.
Using the SCI transporter instead of SCI Sockets is only of interest in communicating between
ndbd
processes. Using the SCI transporter is also only of interest if a CPU can be dedicated to the
ndbd
process because the SCI transporter ensures that this process will never go to sleep. It is also
important to ensure that the
ndbd
process priority is set in such a way that the process does not lose
priority due to running for an extended period of time, as can be done by locking processes to CPUs
in Linux 2.6. If such a configuration is possible, the
ndbd
process will benefit by 10–70% as compared
with using SCI sockets. (The larger figures will be seen when performing updates and probably on
parallel scan operations as well.)
There are several other optimized socket implementations for computer clusters, including Myrinet,
Gigabit Ethernet, Infiniband and the VIA interface. However, we have tested MySQL Cluster so far
only with SCI sockets. See
Section 17.3.5.1, “Configuring MySQL Cluster to use SCI Sockets”
, for
information on how to set up SCI sockets using ordinary TCP/IP for MySQL Cluster.
17.4. MySQL Cluster Programs
Using and managing a MySQL Cluster requires several specialized programs, which we describe
in this chapter. We discuss the purposes of these programs in a MySQL Cluster, how to use the
programs, and what startup options are available for each of them.
These programs include the MySQL Cluster data, management, and SQL node processes (
ndbd
,
ndb_mgmd
, and
mysqld
) and the management client (
ndb_mgm
).
For information about using
mysqld
as a MySQL Cluster process, see
Section 17.5.4, “MySQL Server
Usage for MySQL Cluster”
.
Other
NDB
utility, diagnostic, and example programs are included with the MySQL Cluster distribution.
These include
ndb_restore
,
ndb_show_tables
, and
ndb_config
. These programs are also
covered in this section.
The final portion of this section contains tables of options that are common to all the various MySQL
Cluster programs.
17.4.1.
ndbd
— The MySQL Cluster Data Node Daemon
ndbd
is the process that is used to handle all the data in tables using the NDB Cluster storage engine.
This is the process that empowers a data node to accomplish distributed transaction handling, node
recovery, checkpointing to disk, online backup, and related tasks.
In a MySQL Cluster, a set of
ndbd
processes cooperate in handling data. These processes can
execute on the same computer (host) or on different computers. The correspondences between data
nodes and Cluster hosts is completely configurable.
The following table includes command options specific to the MySQL Cluster data node program
ndbd
. Additional descriptions follow the table. For options common to most MySQL Cluster programs
(including
ndbd
), see
Section 17.4.20, “Options Common to MySQL Cluster Programs — Options
Common to MySQL Cluster Programs”
.
Summary of Contents for 5.0
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