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linux - Swap partition size for 4GB RAM


I'm planning to install Ubuntu 9.04 version. How much space should I dedicate for swap partition. I remember setting it to double the RAM size when I installed long back. At that time my RAM was 256 MB. So I had set the swap partition to 512 MB.



Answer



I would say a good rule of thumb is indeed just as was mentioned above. 2 times the physical memory. Something to consider here, while it is possible to use a smaller swap partition, and it will suffice under most normal circumstances, if you want this system to be rock solid stable, I would indeed follow the 8 GB recommendation. In fact I recommend 2 * RAM + 1 MB so that there is absolutely room to swap out 2 entire copies of memory. This avoids the "shell game" scenario which can have negative performance repercussions. What this will do for you is guarantee a level of resiliency should you encounter an extraordinary event with your system.


I've seen scenarios where applications behave badly in unattended environments and before you know it, your system starts slowing down to a crawl.


Depending on what you are doing, you might even be able to dispense with the swap file entirely. The extra space for the OS is handy when running many applications at once. However if you only intend to run a few processes, do not intend to interact with the GUI disabling the swap file might be appropriate.


But if you are going to have a swap file I always use the sizing formula below.


[(2 x  RAM) + 1 MB] = Swap File Size

I also recommend putting your swap file on a seperate disk whenver possible as this will increase performance as the OS can swap in and out at the same time as read/writes from the data disk.


I hope this is helpful.


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