Linux – swap partition

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.

Modern operating systems require a swap space to make efficient use of RAM. Even if your system has plenty of RAM, wasting RAM results in a smaller buffer cache, which means increased disk I/O. So no matter how much RAM you have, you still want the system to use it efficiently. Using it efficiently means getting things out of RAM that are extremely unlikely to ever be accessed.

When you start up a typical system, a large number of services start up. Programs run initialization code and modify private memory mappings in the process. A number of these services will never run again. Many of them won't run for hours. Without swap, the OS has no choice but to keep the modified private memory mappings associated with those services in RAM forever. That's RAM that can never be used as disk cache.

So you want swap whether you need it or not.