Swap partition size for 4GB RAM

"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."

According to the Ubuntu SwapFAQ here the calculation is 2*MB of RAM. So in this case 8GB. Realistically however you should not need more then 2GB.

The Ubuntu SwapFaq will probably answer a lot of your questions. With larger amounts of RAM you may benefit from changing the default "swappiness" as outlined in this article.