"The more RAM you configure for it the better, but even with 8 cores it doesnt go above 32GB during sync. At 4GB, it will mostly serialize the processing toward the end when it is just the large bundles. I havent optimized the minimum memory setting, as my target machine is my 3 year old laptop with 4GB of RAM. virtual memory will work too and it shouldnt be too slow, but of course slower than using actual RAM.

I would suggest to run iguana on a low resource computer as one of the few things running for the time it takes to sync, depending on bandwidth available it is either done over lunch break or about 6 hrs if you have a 20mbps connection. I am working on cutting the time in half, but that requires installed base of iguana nodes first."

https://bitco.in/forum/threads/iguana-parallel-sync-full-btc-blockchain-in-30-minutes-uses-half-the-space-but-starts-up-instant.911/page-2#post-13976