Oracle 5.0, Справочное руководство

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Using High-Speed Interconnects with MySQL Cluster
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We are working to make sure that communication with the
ndbd
process is made in “chunks” that are
as large as possible because this benefits all types of data transmission.
For users who desire it, it is also possible to use cluster interconnects to enhance performance even
further. There are two ways to achieve this: Either a custom transporter can be designed to handle this
case, or you can use socket implementations that bypass the TCP/IP stack to one extent or another.
We have experimented with both of these techniques using the SCI (Scalable Coherent Interface)
technology developed by
Dolphin Interconnect Solutions .
17.3.5.1. Configuring MySQL Cluster to use SCI Sockets
It is possible employing Scalable Coherent Interface (SCI) technology to achieve a significant increase
in connection speeds and throughput between MySQL Cluster data and SQL nodes. To use SCI, it is
necessary to obtain and install Dolphin SCI network cards and to use the drivers and other software
supplied by Dolphin. You can get information on obtaining these, from
Dolphin Interconnect Solutions .
SCI SuperSocket or SCI Transporter support is available for 32-bit and 64-bit Linux, Solaris, and other
platforms. See the Dolphin documentation referenced later in this section for more detailed information
regarding platforms supported for SCI.
Note
Prior to MySQL 5.0.66, there were issues with building MySQL Cluster with
SCI support (see Bug #25470), but these have been resolved due to work
contributed by Dolphin. SCI Sockets are now correctly supported for MySQL
Cluster hosts running recent versions of Linux using the
-max
builds, and
versions of MySQL Cluster with SCI Transporter support can be built using
either of
compile-amd64-max-sci
or
compile-pentium64-max-
sci
. Both of these build scripts can be found in the
BUILD
directory of the
MySQL Cluster source trees; it should not be difficult to adapt them for other
platforms. Generally, all that is necessary is to compile MySQL Cluster with SCI
Transporter support is to configure the MySQL Cluster build using
--with-
ndb-sci=/opt/DIS
.
Once you have acquired the required Dolphin hardware and software, you can obtain detailed
information on how to adapt a MySQL Cluster configured for normal TCP/IP communication to use SCI
from the from the
Dolphin SCI online documentation .
17.3.5.2. MySQL Cluster Interconnects and Performance
The
ndbd
process has a number of simple constructs which are used to access the data in a MySQL
Cluster. We have created a very simple benchmark to check the performance of each of these and the
effects which various interconnects have on their performance.
There are four access methods:
• Primary key access. This is access of a record through its primary key. In the simplest case, only
one record is accessed at a time, which means that the full cost of setting up a number of TCP/IP
messages and a number of costs for context switching are borne by this single request. In the case
where multiple primary key accesses are sent in one batch, those accesses share the cost of setting
up the necessary TCP/IP messages and context switches. If the TCP/IP messages are for different
destinations, additional TCP/IP messages need to be set up.
• Unique key access. Unique key accesses are similar to primary key accesses, except that a
unique key access is executed as a read on an index table followed by a primary key access on the
table. However, only one request is sent from the MySQL Server, and the read of the index table is
handled by
ndbd
. Such requests also benefit from batching.
• Full table scan. When no indexes exist for a lookup on a table, a full table scan is performed.
This is sent as a single request to the
ndbd
process, which then divides the table scan into a set of
parallel scans on all cluster
ndbd
processes. In future versions of MySQL Cluster, an SQL node will
be able to filter some of these scans.