SWAP分配策略

swap 查询方法:

1 、free 单位KB
2、cat /proc/swaps

swap调整策略

现在服务器内存配置越来越大，以往比较通用的Memory * 1.5的原则基本不再适用，下面是网上收集来的新的分配原则，基于Red Hat Linux的建议，也适合其它Unix。

1）安装系统时难以确定内存的负荷，如何设置交换分区大小

2）系统中物理内存越大，所需交换分区就会越少

因此，在Red Hat Enterprise Linux 5中，以下是设置合适的交换分区大小的规则：

小于等于4G物理内存的系统，至少设置2GB的交换分区

4G〜16G物理内存的系统，至少设置4GB的交换分区

16G〜64G物理内存的系统，至少设置8GB的交换分区

64G〜256G物理内存的系统，至少设置16GB的交换分区

There is no fixed rule to size swap. It depends on the application requirement. The rule of thumb I use is:

if RAM<4GB: swap=2xRAM if RAM is between 4GB - 8GB, swap=RAM if RAM>8GB swap=8GB

The best way is to reserve some disk space for future growth in case you need more swap space and monitor the system.

/var sizing is not related to the physical memory. /var is used to store log, temporary files, spool and core dumps. For example, if the machine is used as mail or print server and it has a lots of messages or print jobs, you need to size /var bigger. Also, when machine crashes, if savecore is enabled, the OS will automatically try to save the kernel dump to /var/crash directory. 10G is kind of overkill but it doesn't hurt as long as you have enough space.