I have Linux server and I have a spare 500GB disk partition. I wanted to format it and use it for /tmp. The server occasionally runs some large data processing tasks so it can happen that /tmp will hold GBs of temporary data.
Then I got an idea that instead I could add it as a swap partition instead and mount /tmp to tmpfs. Is this idea reasonable?
The server has 6GB of RAM, so in most cases data on /tmp would be only in RAM, with the obvious speed advantage. The question is, what if there will be let's say 10-20GB of data on /tmp, how will the system perform? What would be the performance compared to having simply /tmp mounted to an ext4 partition? Thanks for help.
Edit: It is clear that the system will start swapping out memory when the usage of tmpfs hits the RAM limit. But is Linux smart enough to swap out tmpfs data and keep "regular" data in RAM? If yes, then I suppose it could behave reasonably. If not, then the whole system will be severely affected.
Best Answer
This is NOT A Good IdeaTM.
You'll be fine with a large
/tmppartition, mounted like this (from your/etc/fstab)And you could add your external drive as a giant swap partition
When that hits its limit, your machine will start to swap the pages from RAM to disk - at which point, load averages will go through the roof and the machine will grind to a halt.
Its a bad idea to rely on SWAP in any way, you'd be better off selling your 500GB drive and simply buying more RAM - its cheap.
In summary
If you really want to use your 500GB disk, you could mount your 500GB disk on
/tmpwith a non-journaled filesystem with atime and diratime disabled (eg.ext2). That would be substantially faster than dealing with a machine that isSWAPing