關於Swap分區

Swap分區tip（摘自Redhat官方文檔）

Swap should equal 2x physical RAM for up to 2 GB of physical RAM, and then 1x physical RAM for any amount above 2 GB, but never less than 32 MB. 

Using this formula, a system with 2 GB of physical RAM would have 4 GB of swap, while one with 3 GB of physical RAM would have 5 GB of swap. Creating a large swap space partition can be especially helpful if you plan to upgrade your RAM at a later time. 

Tip      

If your partitioning scheme requires a swap partition that is larger than 2 GB, you should create an additional swap partition. For example, if you need 4 GB of swap, you should create two 2 GB swap partitions. If you have 4 GB of RAM, you should create three 2 GB swap partitions. Red Hat Enterprise Linux supports up to 32 swap files. 

For systems with really large amounts of RAM (more than 32 GB) you can likely get away with a smaller swap partition (around 1x, or less, of physical RAM). 

翻譯 :當物理內存小於2G時，swap大小爲物理內存的2倍。當物理內存大於2G，超過2G的部分，swap大小跟物理內存相等。

即：

    x<=2G的部分, swap=2x；

    x>2G的部分, swap= (2*2G)+( x-2G)

利用這個法則，2G物理內存須要4G swap，而3G物理內存則須要5G swap。若是你打算添加內存的話，建立一個大些的swap區是頗有幫助的。

Tip
若是按照分區計劃，你的swap區超過2GB，那麼應該建立另外的swap分區。
好比，你須要4GB的swap的分區，應該建立2個2GB的swap分區。

若是有4GB的物理內存，則應該建立3個2GB的swap分區。

Redhat EL支持多達32個swap文件。

分析：2GB的物理內存 須要swap 2x2GB=4GB，
超過2GB的2GB 須要swap 1x2GB=2GB。
總共6G，每一個swap分區2G，因此是3個2GB的swap分區

對於超過32G物理內存的，使用小於等於物理內存容量的swap區會更好。

轉自：http://tanyear.spaces.live.com/blog/cns!AEF791CD8FBB4AF8!203.entry