How much swap space do you allocate on Linux?

"IBM InfoSphere Balanced Warehouse D5100: Design and Implementation Guide", if I'm reading it correctly, still suggests 1:1 (32GB of swap for 32GB of RAM). In addition, the following is recommended:

" The file-system cache-related configuration parameters can be found in
the /proc/sys/vm file. The recommended values for the file-system caching
parameters are as follows:
v swappiness: 0
v dirty_ratio: 10
v dirty_background_ratio: 5 "

Hi Bella,

we usally don't use a 1:1. Mostly we use 1:8 on Linux. Mostly we have 2 - 4 GB Swap per Server. Even on Systems with 64 GB RAM and we never ran into issues.

Windows requires at least a 1:1 ratio for Pagefile.

I agree with nvk@vhv. The 1:1 was required a long time ago for AIX systems (and maybe Linux) when max system memory was typcially much smaller.

We also have used these with sucesss on all our OLTP systems:

- swappiness: 0
- dirty_ratio: 10
- dirty_background_ratio: 5

Linux tends to do too much swapping for file system cache without these.