I need to hugely extend RAM in the platform I can't do it. As a temporary solution I want to use swap for it. What is better to use for swap storage - an SSD or 15k HDD like Cheetah? I understand that anyway it'll be slower than RAM.
disclaimer: i've never tried it.
gut feeling tells me ssd will do a better job and ... will die much sooner in the process - it offers much higher number of i/o's per second than physical hard drive [even if it's 15k rpm it's still 250 seeks/sec vs thousand or more]. but... hard drive will have much smaller addressable block - probably 512B, while ssd will have to erase 16-64kB even if single bit is changed in the swapped page.
The SSD will do a better job than a single 15k disk. Can you provide some numbers, though? Have you already exhausted the swap on your system?
If the need to extend RAM on the platform is important enough for you to care about SWAP performance, then it's probably important enough to obtain the right amount of RAM.