When a core dump is taken:
- The kernel saves the core dump and control information to swap space.
- On boot, rc(8) executes savecore(8) to copy any core dumps to /var/swap.
If you want diagnostic information captured when the kernel panics, you will need sufficient swap space so that the kernel can capture the dump. The savecore(8) program will not copy the dump from swap to /var/crash if there is insufficient space.
Since you don't want to capture diagnostic information on any failures, you need not retain space in /var for a core dump.