ctdb/web/index.html

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   4 <H2 align="center">Welcome to the CTDB web pages</H2>
   5
   6 CTDB is a cluster implementation of the TDB database used by Samba and
   7 other projects to store temporary data. If an application is already
   8 using TDB for temporary data it is very easy to convert that
   9 application to be cluster aware and use CTDB instead.
  10
  11 <p>CTDB provides the same types of functions as TDB but in a clustered
  12   fashion, providing a TDB-style database that spans multiple physical
  13   hosts in a cluster.
  14
  15 <p>Features include:
  16 <ul>
  17 <li>CTDB provides a TDB that has consistent data and consistent locking across
  18 all nodes in a cluster.
  19 <li>CTDB is very fast.
  20 <li>In case of node failures, CTDB will automatically recover and
  21   repair all TDB databases that it manages.
  22 <li>CTDB is the core component that provides <strong>pCIFS</strong>
  23 ("parallel CIFS") with Samba3/4.
  24 <li>CTDB provides HA features such as node monitoring, node failover,
  25   and IP takeover.
  26 <li>CTDB provides a reliable messaging transport to allow applications
  27  linked with CTDB to communicate to other instances of the application
  28  running on different nodes in the cluster.
  29 <li>CTDB has pluggable transport backends. Currently implemented backends are TCP
  30  and Infiniband.
  31 <li>CTDB supports a system of application specific management scripts,
  32   allowing applications that depend on network or filesystem resources
  33   to be managed in a highly available manner on a cluster.
  34 </ul>
  35
  36 <h2>Requirements</h2>
  37
  38 CTDB relies on a clustered filesystem being available and shared on
  39 all nodes that participate in the CTDB cluster. This filesystem must
  40 be mounted and available on all nodes in the CTDB cluster.
  41
  42 <p>On top of this cluster filesystem, CTDB then provides clustered HA
  43 features so that data from the clustered filesystem can be exported
  44 through multiple nodes in the CTDB cluster using various
  45 services. Currently included with CTDB are the necessary hooks for Samba, NFS
  46   and ftp exports. Support for new service types can easily be added.
  47
  48 <h2>TDB</h2>
  49
  50 TDB is a very fast simple database that was originally developed for
  51 use in Samba. Today several other projects use TDB to store their data.
  52
  53 <p>See the <a
  54 href="http://samba.org/ftp/unpacked/tdb/docs/README">TDB
  55 README file</a> for a description of how TDB is used.
  56
  57 <h2>Documentation</h2>
  58
  59 <a href="./documentation.html">CTDB documentation</a><br><br>
  60
  61 Additional documentation on how to install and configure CTDB is available in the
  62 <a href="http://wiki.samba.org/index.php/CTDB_Setup">CTDB
  63   Wiki</a>. Please read all of the documentation carefully.
  64
  65 <h2>High Availability Features</h2>
  66
  67 The CTDB nodes in a cluster designates one node as a recovery master
  68 through an election process. If the recovery master node fails a
  69 new election is initiated so that the cluster will always guarantee
  70 there will be a recovery master. The recovery master will
  71 continuously monitor the cluster to verify that all nodes contain a
  72 consistent configuration and view of the cluster and will initiate a
  73 recovery process when required.
  74
  75 <p>During the recovery phase, the recovery master will automatically
  76 rebuild/recover all clustered TDB database to ensure that the
  77 databases are consistent. Recovery typically takes between 1 and 3
  78 seconds. During the recovery period the databases are 'frozen', and
  79 all database IO operations by ctdb clients are suspended.
  80
  81 <h3>Is CTDB a HA solution?</h3>
  82
  83 Yes and no.<p>
  84
  85 CTDB alone is not a HA solution, but when you combine CTDB with a clustered
  86 filesystem it becomes one.<p>
  87
  88 CTDB is primarily developed around the concept of having a shared
  89 cluster filesystem across all the nodes in the cluster to provide the
  90 features required for building a NAS cluster.<p>
  91
  92 Thus CTDB relies on an external component (the cluster filesystem) to
  93 provide the mechanisms for avoiding split-brain and other core
  94 clustering tasks.<p>
  95
  96 However, if you do have a clustered filesystem for all the nodes, in
  97 that scenario CTDB will provide a very easy to install and manage
  98 solution for your clustering HA needs.
  99
 100 <h3>IP Takeover</h3>
 101
 102 When a node in a cluster fails, CTDB will arrange that a different
 103 node takes over the IP address of the failed node to ensure that the
 104 IP addresses for the services provided are always available.
 105
 106 <p>To speed up the process of IP takeover and when clients attached to
 107 a failed node recovers as fast as possible, CTDB will automatically
 108 generate gratuitous ARP packets to inform all nodes of the changed MAC
 109 address for that IP.  CTDB will also send "tickle ACK" packets to all
 110 attached clients to trigger the clients to immediately recognize that
 111 the TCP connection needs to be re-established and to shortcut any TCP
 112 retransmission timeouts that may be active in the clients.
 113
 114 <h2>Discussion and bug reports</h2>
 115
 116 For discussions please use
 117 the <a href="https://lists.samba.org/mailman/listinfo/samba-technical">samba-technical</a>
 118 mailing list. To submit a bug report, please use
 119 the <a href="http://bugzilla.samba.org/">Samba bugzilla</a> bug
 120 tracking system.
 121
 122 <p>We would be very interested in hearing from and work with other
 123 projects that want to make their services cluster aware using CTDB.
 124
 125 <p>CTDB discussions also happen on the #ctdb IRC channel on freenode.net
 126
 127
 128 <hr>
 129 <h2>Developers</h2>
 130 <ul>
 131 <li><a href="http://samba.org/~tridge/">Andrew Tridgell</a></li>
 132 <li><a href="http://samba.org/~sahlberg/">Ronnie Sahlberg</a></li>
 133 <li><a href="http://samba.org/~obnox/">Michael Adam</a></li>
 134 <li>Peter Somogyi</li>
 135 <li><a href="http://sernet.de/Samba/">Volker Lendecke</a></li>
 136 <li>Stefan Metzmacher</li>
 137 <li><a href="http://meltin.net/people/martin/">Martin Schwenke</a></li>
 138 <li>Amitay Isaacs</li>
 139 </ul>
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