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| From: | jon | Date: | May 18 2007 12:03pm |
| Subject: | svn commit - mysqldoc@docsrva: r6524 - trunk/refman-5.0 | ||
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Author: jstephens Date: 2007-05-18 12:03:14 +0200 (Fri, 18 May 2007) New Revision: 6524 Log: Reworking 5.0 Cluster Limitations: next 2 subsections. Modified: trunk/refman-5.0/mysql-cluster-limitations-working.xml Modified: trunk/refman-5.0/mysql-cluster-limitations-working.xml =================================================================== --- trunk/refman-5.0/mysql-cluster-limitations-working.xml 2007-05-18 10:02:04 UTC (rev 6523) +++ trunk/refman-5.0/mysql-cluster-limitations-working.xml 2007-05-18 10:03:14 UTC (rev 6524) Changed blocks: 2, Lines Added: 211, Lines Deleted: 104; 12787 bytes @@ -742,108 +742,6 @@ </listitem> - <listitem> - <indexterm> - <primary>MySQL Cluster limitations</primary> - <secondary>implementation</secondary> - </indexterm> - - <para id="mysql-cluster-limitations-exclusive-to-cluster"> - <emphasis role="bold">Issues exclusive to MySQL - Cluster</emphasis> (not related to <literal>MyISAM</literal> - or <literal>InnoDB</literal>): - </para> - - <itemizedlist> - - <listitem> - <para> - All machines used in the cluster must have the same - architecture. That is, all machines hosting nodes must be - either big-endian or little-endian, and you cannot use a - mixture of both. For example, you cannot have a management - node running on a PowerPC which directs a data node that - is running on an x86 machine. This restriction does not - apply to machines simply running <command>mysql</command> - or other clients that may be accessing the cluster's SQL - nodes. - </para> - </listitem> - - <listitem> - <para> - It is also not possible to perform a Cluster backup and - restore between different architectures. For example, you - cannot back up a cluster running on a big-endian platform - and then restore from that backup to a cluster running on - a little-endian system. (Bug #19255) - </para> - </listitem> - - <listitem> - <para> - It is not possible to make online schema changes such as - those accomplished using <literal>ALTER TABLE</literal> or - <literal>CREATE INDEX</literal>, as the <literal>NDB - Cluster</literal> engine does not support autodiscovery of - such changes. (However, you can import or create a table - that uses a different storage engine, and then convert it - to <literal>NDB</literal> using <literal>ALTER TABLE - <replaceable>tbl_name</replaceable> - ENGINE=NDBCLUSTER</literal>. In such a case, you must - issue a <literal>FLUSH TABLES</literal> statement to force - the cluster to pick up the change.) - </para> - </listitem> - - <listitem> - <para> - Online adding or dropping of nodes is not possible (the - cluster must be restarted in such cases). - </para> - </listitem> - - <listitem> - <para> - Multiple network addresses per data node are not - supported. Use of these is liable to cause problems: In - the event of a data node failure, an SQL node waits for - confirmation that the data node went down but never - receives it because another route to that data node - remains open. This can effectively make the cluster - inoperable. - </para> - - <para> - It is possible to use multiple network hardware interfaces - (such as Ethernet cards) for a single data node, but these - must be bound to the same address. This also means that it - not possible to use more than one <literal>[TCP]</literal> - section per connection in the - <literal>config.ini</literal> file. See - <xref linkend="mysql-cluster-tcp-definition"/>, for more - information. - </para> - </listitem> - - <listitem> - <para> - The maximum number of data nodes is 48. - </para> - </listitem> - - <listitem> - <para> - The total maximum number of nodes in a MySQL Cluster is - 63. This number includes all SQL nodes (MySQL Servers), - API nodes (applications accessing the cluster other than - MySQL servers), data nodes, and management servers. - </para> - </listitem> - - </itemizedlist> - </listitem> - </itemizedlist> <section id="mysql-cluster-limitations-syntax"> @@ -871,11 +769,220 @@ </section> <section id="mysql-cluster-limitations-performance"> - <title></title> + + <title>Limitations Relating to Performance</title> + + <indexterm> + <primary>MySQL Cluster limitations</primary> + <secondary>performance</secondary> + </indexterm> + + <para> + The following performance issues are specific to or especially + pronounced in MySQL Cluster: + + <itemizedlist> + + <listitem><formalpara> + <title>Range scans</title> + <para> + There are query performance issues due to sequential access + to the <literal>NDB</literal> storage engine; it is also + relatively more expensive to do many range scans than it is + with either <literal>MyISAM</literal> or + <literal>InnoDB</literal>. + </para></formalpara> + </listitem> + + <listitem> + <formalpara> + <title>Reliability of <literal>Records in range</literal></title> + <para> + The <literal>Records in range</literal> statistic is + available but is not completely tested or officially + supported. This may result in non-optimal query plans in + some cases. If necessary, you can employ <literal>USE + INDEX</literal> or <literal>FORCE INDEX</literal> to alter + the execution plan. See <xref linkend="index-hints"/>, for + more information on how to do this. + </para></formalpara> + </listitem> + + <listitem> + <formalpara> + <title>Unique hash indexes</title> + <para> + Unique hash indexes created with <literal>USING + HASH</literal> cannot be used for accessing a table if + <literal>NULL</literal> is given as part of the key. + </para></formalpara> + </listitem> + + <listitem> + <formalpara> + <title>Binary logging</title> + <para> + MySQL Cluster has the following limitations or + restrictions with regard to binary logging: + + <itemizedlist> + <listitem> + <para> + <literal>SQL_LOG_BIN</literal> has no effect on data + operations; however, it is supported for schema operations. + </para> + + </listitem> + + <listitem> + + <para> + MySQL Cluster cannot produce a binlog for tables having + <literal>BLOB</literal> columns but no primary key. + </para> + </listitem> + + <listitem> + <para> + Only the following schema operations are logged in a cluster + binlog which is <emphasis>not</emphasis> on the + <command>mysqld</command> executing the statement:<itemizedlist> + + <listitem> + <para> + <literal>CREATE TABLE</literal> + </para> + </listitem> + + <listitem> + <para> + <literal>ALTER TABLE</literal> + </para> + </listitem> + + <listitem> + <para> + <literal>DROP TABLE</literal> + </para> + </listitem> + + <listitem> + <para> + <literal>CREATE DATABASE</literal> / <literal>CREATE + SCHEMA</literal> + </para> + </listitem> + + <listitem> + <para> + <literal>DROP DATABASE</literal> / <literal>DROP + SCHEMA</literal> + </para> + </listitem> + + </itemizedlist> + </para> + </listitem> + </itemizedlist> + + </para> + </formalpara> + + + + + + + </listitem> + + </itemizedlist> + </para> </section> <section id="mysql-cluster-limitations-exclusive-to-cluster"> - <title></title> + + <title>Issues Exclusive to MySQL Cluster</title> + + <indexterm> + <primary>MySQL Cluster limitations</primary> + <secondary>implementation</secondary> + </indexterm><para> + The following are limitations specific to the + <literal>NDBCLUSTER</literal> storage engine, and do not occur + with <literal>MyISAM</literal> or <literal>InnoDB</literal>: + <itemizedlist> + + <listitem><formalpara> + <title>Machine architecture</title> + <para> + The following issues relate to physical architecture of + cluster hosts: + <itemizedlist> + <listitem> + <para> + All machines used in the cluster must have the same + architecture. That is, all machines hosting nodes must be + either big-endian or little-endian, and you cannot use a + mixture of both. For example, you cannot have a management + node running on a PowerPC which directs a data node that + is running on an x86 machine. This restriction does not + apply to machines simply running <command>mysql</command> + or other clients that may be accessing the cluster's SQL + nodes. + </para> + </listitem> + + <listitem> + <formalpara> + + <title>Adding and dropping of data nodes</title> + + <para> + Online adding or dropping of data nodes is not currently + possible. In such cases, the entire cluster must be + restarted. + </para> + + </formalpara> + </listitem> + + <listitem><formalpara> + + <title>Backup and restore between architectures</title> + <para> + It is also not possible to perform a Cluster backup and + restore between different architectures. For example, you + cannot back up a cluster running on a big-endian platform + and then restore from that backup to a cluster running on + a little-endian system. (Bug #19255) + </para></formalpara> + </listitem> + </itemizedlist> + + </para> + </formalpara> + </listitem> + + <listitem> + <formalpara> + <title>Online schema changes</title> + <para> + It is not possible to make online schema changes such as + those accomplished using <literal>ALTER TABLE</literal> or + <literal>CREATE INDEX</literal>, as the <literal>NDB + Cluster</literal> engine does not support autodiscovery of + such changes. (However, you can import or create a table + that uses a different storage engine, and then convert it + to <literal>NDB</literal> using <literal>ALTER TABLE + <replaceable>tbl_name</replaceable> + ENGINE=NDBCLUSTER</literal>. In such a case, you must + issue a <literal>FLUSH TABLES</literal> statement to force + the cluster to pick up the change.) + </para></formalpara> + </listitem> + </itemizedlist> + + </para> </section> <section id="mysql-cluster-limitations-multiple-nodes">
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| • svn commit - mysqldoc@docsrva: r6524 - trunk/refman-5.0 | jon | 18 May |
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