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A basic installation contains at least 2 database servers and 1 monitoring server. In this guide, I used 5 servers with Debian Lenny (5.0)

I used the following virtual IPs. They will be distributed across the hosts by MMM.

一、MMM简介：

MMM即Master-Master Replication Manager for MySQL（mysql主主复制管理器）关于mysql主主复制配置的监控、故障转移和管理的一套可伸缩的脚本套件（在任何时候只有一个节点可以被写入），这个套件也能对居于标准的主从配置的任意数量的从服务器进行读负载均衡，所以你可以用它来在一组居于复制的服务器启动虚拟ip，除此之外，它还有实现数据备份、节点之间重新同步功能的脚本。

MySQL本身没有提供replication failover的解决方案，通过MMM方案能实现服务器的故障转移，从而实现mysql的高可用。

MMM项目来自 Google：http://code.google.com/p/mysql-master-master

官方网站为：http://mysql-mmm.org

Mmm主要功能由下面三个脚本提供

lmmm_mond负责所有的监控工作的监控守护进程，决定节点的移除等等

lmmm_agentd运行在mysql服务器上的代理守护进程，通过简单远程服务集提供给监控节点

lmmm_control通过命令行管理mmm_mond进程

 Last month we released the Beta of VS 2010 Service Pack 1 (SP1). You can learn more about the VS 2010 SP1 Beta from Jason Zander’s twoblog posts about it, and from Scott Hanselman’s blog post that covers some of the new capabilities enabled with it. You can download and install the VS 2010 SP1 Beta here.

Last week I blogged about the new Visual Studio support for IIS Express that we are adding with VS 2010 SP1. In today’s post I’m going to talk about the new VS 2010 SP1 tooling support for SQL CE, and walkthrough some of the cool scenarios it enables.

.NET Compact Framework Data Provider for SQL Server Mobile

症状：

mysql数据库无法正常启动，日志如下：

111110 14:41:22  InnoDB: Starting shutdown...
111110 14:41:28  InnoDB: Shutdown completed; log sequence number 0 103559
111110 14:41:28 [Note] MySQL: Shutdown complete

111110 14:43:06 [Note] Plugin 'FEDERATED' is disabled.
111110 14:43:06  InnoDB: Started; log sequence number 0 103559
111110 14:43:06 [ERROR] Binlog has bad magic number;  It's not a binary log file that can be used by this version of MySQL
111110 14:43:06 [ERROR] Can't init tc log
111110 14:43:06 [ERROR] Aborting

111110 14:43:06  InnoDB: Starting shutdown...
111110 14:43:11  InnoDB: Shutdown completed; log sequence number 0 103559
111110 14:43:11 [Note] MySQL: Shutdown complete

解决办法：

删除最后一个mysql-bin.x，打开mysql-bin.index 文件，删除对应的mysql-bin.x条目，重启。（未经测试）

Until Informix Dynamic Server 10.0 the number of MSC (or Miscellaneous) Virtual Processors was limited to one. With IDS 10.0 multiple MSC VPs can be configured using the VPCLASS onconfig parameter (e.g. VPCLASS msc,num=2), or added dynamically using onmode -p 1 msc.

What does that mean and why would I want to use it?
The MSC VP is a type of AIO VP, executing operating system calls on behalf of other threads. While the AIO VP mainly takes care of filesystem I/O calls the MSC VP executes some network and authentication calls like getpwnam(), gethostbyname(), gethostbyaddr() etc. (It also maintains some statistics like VP CPU usage.) The MSC VP gets used at client connection time for the operating system part of user validation, and in most cases one is sufficient.

Virtual Processor (VP) is the technical term for an Informix process. Informix forks off a handful of these VPs at engine startup to take advantage of multiple CPUs or cores and increase parallelism. Each VP is multithreaded allowing Informix to efficiently use the CPU time each process is awarded by the OS, letting ready threads do work while other threads are busy waiting on something else to finish.

There are multiple types of VPs, each performing a specific job. Some VPs are configurable (i.e. the number of VPs and what CPU they should run on, etc.) through the VPCLASS ONCONFIG parameter and some are not. The 2 VPs you need to be concerned about right now are:

• CPU - Runs all session threads and some system threads. Runs KAIO (Kernel Asynchronous I/O) if enabled. This process will consume most of the CPU cycles given to Informix by the OS and is configurable.
• AIO - Performs all I/O except for physical or logical logging if KAIO is disabled. Performs I/O to cooked chunks if KAIO is enabled and is configurable.

环境配置及症状：

AS4U8+IDS9.21.UC2

$ONCONFIG

ALARMPROGRAM    /home/informix/etc/log_full.sh # Alarm program path

bar_act.log

 2011-10-14 13:48:40 8063  8061 /home/informix/bin/onbar_d -b -l
 2011-10-14 13:48:40 8063  8061 Begin backup logical log 311991.
 2011-10-14 13:48:40 8063  8061 Successfully connected to Storage Manager.
 2011-10-14 13:48:40 8063  8061 ASSERT: file bar_xbsa.ecbarSendData() line 1331 - contact product support
 2011-10-14 13:48:40 8063  8061 See also: /home/informix/tmp/core

online.log

13:48:39  Logical Log 311993 Complete.
13:48:40  Logical Log 311991 - Backup Started
13:48:40  Logical Log 311991 - Backup Aborted
          Aborted by client.
13:48:40  Process exited with return code 139: /bin/sh /bin/sh -c /home/informix/etc/log_full.sh 2 23 "Logical Log 311993 Complete." "Logical Log 311993 Complete."

系统逻辑日志满时，自动触发/home/informix/etc/log_full.sh 进行逻辑日志备份，bar_act.log及online.log日志信息如上（手工进行逻辑日志备份正常）