当你听到memcache与memcached时把它当做是一个东东就好了，尽管它们存在区别，但是这并不影响你对它们的运用及理解。
“Memcache”它是一个自由和开放源代码、高性能、分配的内存对象缓存系统，即该系统名称为“Memcache”;
“Memcached”它是该系统的主程序文件，以守护程序方式运行于一个或多个服务器中（分布式），随时接受客户端的连接操作，使用共享内存存取数据;
“Memcachedb”它是新浪2007年的项目，在Memcached的基础上开发出来了，它与Memcache不同的是它提供了数据持久化存储
首先，我们需要下载一个memcached安装程序，memcached版本很多，开源的东西我们一定要找一个持续更新的版本，很简单，有团队在维护升级。
我选择的版本是：beitmemcached，项目地址：http://code.google.com/p/beitmemcached/ 注：此链结为windows下memcached文程序安装文件及示例。
图中的两个文件分别为：上面的是客户端调用示例项目文件、下面的文件是Memcached主程序安装文件
然后，将memcached主程序文件安装到服务器上。
Windows下安装：
1.将上图中Memcached 1.2.5.zip解压缩到 D:\program files\memcached目录下（此目录自行定义）。
2.Ctrl+R，输入cmd，打开命令行窗口，转到D:\program files\memcached目录下。
3.memcached.exe -d install
4.memcached.exe -d start
如果你要卸载，执行下面的命令：
1.memcached.exe -d stop
2.memcached.exe -d uninstall
Linux（CentOS 5.x）下安装：
1. yum install gcc
2. cd /tmp
3. wget http://www.monkey.org/~provos/libevent-2.0.4-alpha.tar.gz 注：memcached 用到了 libevent 这个库用于 Socket 的处理，所以 还需要安装 libevent
4. tar zxvf libevent-2.0.4-alpha.tar.gz
5. cd libevent-2.0.4-alpha
6. ./configure -prefix=/usr/local/libevent
7. make
8. make install
9. cd ~
10. cd /tmp
11. http://memcached.googlecode.com/files/memcached-1.4.5.tar.gz
12. tar zxvf memcached-1.4.5.tar.gz
13. cd memcached-1.4.5
14. ./configure -prefix=/usr/local/memcached --with-libevent=/usr/local/libevent 注：安装memcached时需要指定libevent的安装位置
15. make
16. make install
17. export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/libevent/lib 注：将libevent的lib目录加入LD_LIBRARY_PATH里
18. vi /etc/sysconfig/iptables
19. 将下面这行加入进去
-A RH-Firewall-l-INPUT -p tcp -m tcp --dport 11211 -j ACCEPT 注：将memcached加入到防火墙允许访问规则中
20. service iptables restart 注：防火墙重启
21. /usr/local/memcached/bin/memcached -d 注：启动memcached
memcached启动参数描述：
-d ：启动一个守护进程，
-m：分配给Memcache使用的内存数量，单位是MB，默认是64MB，
-u ：运行Memcache的用户
-l ：监听的服务器IP地址
-p ：设置Memcache监听的端口，默认是11211 注：-p（p为小写）
-c ：设置最大并发连接数，默认是1024
-P ：设置保存Memcache的pid文件 注：-P（P为大写）
如果要结束Memcache进程，执行：kill cat pid文件路径
无论是在windows下还是在linux下安装都非常简单，使用起来也很简单。
如何往memcached中插入数据？如何来读取数据？示例代码如下：
代码
using System;
using System.Collections.Generic;
namespace BeIT.MemCached {
class Example {
public static void Main(string[] args) {
//---------------------
// Setting up a client.
//---------------------
Console.Out.WriteLine("Setting up Memcached Client.");
MemcachedClient.Setup("MyCache", new string[] { "localhost" });
//It is possible to have several clients with different configurations:
//If it is impossible to resolve the hosts, this method will throw an exception.
try {
MemcachedClient.Setup("MyOtherCache", new string[]{ "server1.example.com:12345", "server2.example.com:12345"});
} catch (Exception e) {
Console.WriteLine(e.Message);
}
//Get the instance we just set up so we can use it. You can either store this reference yourself in
//some field, or fetch it every time you need it, it doesn't really matter.
MemcachedClient cache = MemcachedClient.GetInstance("MyCache");
//It is also possible to set up clients in the standard config file. Check the section "beitmemcached"
//in the App.config file in this project and you will see that a client called "MyConfigFileCache" is defined.
MemcachedClient configFileCache = MemcachedClient.GetInstance("MyConfigFileCache");
//Change client settings to values other than the default like this:
cache.SendReceiveTimeout = 5000;
cache.ConnectTimeout = 5000;
cache.MinPoolSize = 1;
cache.MaxPoolSize = 5;
//----------------
// Using a client.
//----------------
//Set some items
Console.Out.WriteLine("Storing some items.");
cache.Set("mystring", "The quick brown fox jumped over the lazy dog.");
cache.Set("myarray", new string[]{"This is the first string.", "This is the second string."});
cache.Set("myinteger", 4711);
cache.Set("mydate", new DateTime(2008, 02, 23));
//Use custom hash
cache.Set("secondstring", "Flygande b鋍kasiner s鰇a hwila p?mjuka tufvor", 4711);
//Get a string
string str = cache.Get("mystring") as string;
if (str != null) {
Console.Out.WriteLine("Fetched item with key: mystring, value: " + str);
}
//Get an object
string[] array = cache.Get("myarray") as string[];
if (array != null) {
Console.Out.WriteLine("Fetched items with key: myarray, value 1: " + array[0] + ", value 2: " + array[1]);
}
//Get several values at once
object[] result = cache.Get(new string[]{"myinteger", "mydate"});
if (result[0] != null && result[0] is int) {
Console.Out.WriteLine("Fetched item with key: myinteger, value: " + (int)result[0]);
}
if (result[1] != null && result[1] is DateTime) {
Console.Out.WriteLine("Fetched item with key: mydate, value: " + (DateTime)result[1]);
}
str = cache.Get("secondstring", 4711) as string;
if (str != null) {
Console.Out.WriteLine("Fetched item with key and custom hash: secondstring, value: " + str);
}
//Set a counter
Console.Out.WriteLine("Setting an item for incrementing and decrementing.");
cache.SetCounter("mycounter", 9000);
ulong? counter = cache.GetCounter("mycounter");
if (counter.HasValue) {
Console.Out.WriteLine("Fetched mycounter, value: " + counter.Value);
}
//Increment the counter
counter = cache.Increment("mycounter", 1);
if (counter.HasValue) {
Console.Out.WriteLine("Incremented mycounter with 1, new value: " + counter.Value);
}
//Decrement the counter
counter = cache.Decrement("mycounter", 9000);
if (counter.HasValue) {
Console.Out.WriteLine("Decremented mycounter with 9000, new value: " + counter.Value);
}
//Append and prepend
Console.Out.WriteLine("Storing bar for append/prepend");
cache.Set("foo", "bar");
Console.Out.WriteLine("Appending baz");
cache.Append("foo", " baz");
Console.Out.WriteLine("Prepending foo");
cache.Prepend("foo", "foo ");
Console.Out.WriteLine("New value: " + cache.Get("foo"));
//Cas
cache.Delete("castest");
Console.Out.WriteLine("Trying to CAS non-existant key castest: " + cache.CheckAndSet("castest", "a", 0));
Console.Out.WriteLine("Setting value for key: castest, value: a");
cache.Set("castest", "a");
Console.Out.WriteLine("Trying to CAS key castest with the wrong unique: " + cache.CheckAndSet("castest", "a", 0));
ulong unique;
cache.Gets("castest", out unique);
Console.Out.WriteLine("Getting cas unique for key castest: " + unique);
Console.Out.WriteLine("Trying to CAS again with the above unique: " + cache.CheckAndSet("castest", "b", unique));
string value = cache.Gets("castest", out unique) as string;
Console.Out.WriteLine("New value: " + value + ", new unique: " + unique);
Console.Out.WriteLine("Displaying the socketpool status:");
foreach (KeyValuePair<string, Dictionary<string, string>> host in cache.Status()) {
Console.Out.WriteLine("Host: " + host.Key);
foreach (KeyValuePair<string, string> item in host.Value) {
Console.Out.WriteLine("\t" + item.Key + ": " + item.Value);
}
Console.Out.WriteLine();
}
Console.Out.WriteLine();
Console.Out.WriteLine("Finished. Press enter to exit.");
Console.In.ReadLine();
}
}
}
注：memcached是以KEY-VALUE的方式进行数据存储的，KEY的大小限制：Key（max）<=250个字符；VALUE在存 储时有限制：Value（max）<= 1M；memcached默认过期时间：ExpiresTime（max）= 30（days）。
