Swap is only used when you run out of memory and will slow down your system in a way you think it’s frozen. As this should not happen for this reason to often I would recommend either to put it on the SSD or even better to think about a swap file.
Why making it complicated? Do you have a good reason for that idea? Simplest approach is to only have / partition (of 25 - 50 GiB) and if you want to get some easy way to backup or recover the system mabybe have a separate /home partition with rest of available disk space. The /home partition could be on the HDD.
In Manjaro, /tmp is not an on-disk filesystem but a tmpfs, which is a filesystem that lives in virtual memory, although its contents can be paged out to the swap partition if need be.
Having your swap partition on a spinning rust drive is not a bad idea, depending on how much RAM you have in your machine, and how you use that machine. I myself have quite a lot of multitasking going on here, and my machine has 16 GiB of RAM. I’ve disabled swap quite a while ago, and yet I’m never running out of memory.
Either way, apart from swap, for everything else, you don’t need to worry anymore. Modern SSDs come with a massively over-provisioned storage capacity for wear-leveling purposes, so they don’t wear out so easily anymore as the early SSDs did. To give you but one example, a Samsung 1 TB SSD ─ of which I own one ─ can handle about 400 TB worth of writes before it wears out.
In regards to swap, I will not be using hibernation, so the size of that partition should be reduced considerably, and /home was always intended to be on the HDD, separate from any OS so that nothing is lost in the event of OS problems.
Thank you for the tip on directories being resident in RAM - I was unsure of these. The tmp and temp folders in Windows can grow to stupid sizes due to not being automatically purged!
However, I have read about /var filling up quickly, which suggests multiple background writes. Is this likely to be a problem?
That, plus that the Windows filesystem drivers do not allocate free space intelligently, which quickly results in fragmentation. Conversely, the Linux filesystem drivers intelligently store files based upon the amount of contiguous free space.
This is because during an update or the installation of additional packages, pacman downloads the packages to /var/cache/pacman/pkg/, and it does not empty that cache by default. Good system maintenance includes the regular deletion of those packages. See…
Exactly and it’s something I do routinely when upgrading this or one of the other systems (a practice learned after a few hiccups) … check available disk space first & delete the stuff in tha cache (in my case, manually) when necessary before performing a System Upgrade or indeed installing any software which might need the space.