You can do a few things to mitigate coin applications that cause problems:
1. Lower the CPU affinity and process priority. You can do this with task manager right-clicks in Windows if you are going to leave Bitcoin running, or you can make a .cmd file (batch file) to run with the start priority options. CPU is required to validate P2P transaction signatures, and someone could be targeting you specifically with attack transaction broadcasts.
2. If your rotating hard disk is fragmented, that means the disk heads will have to hunt all over the platter to find data, limiting the possible input-output operations per second. You can use defrag programs that completely move and defrag every file, but the new blocks every 10 minutes will again be fragmented. It would be best to give the Bitcoin datadir its own ~40gb disk partition to limit hunting. This problem is solved with a SSD - instead of a limit of 150 IOPS from moving heads, it's more like 40000 IOPS.
3. Monitor RAM usage. I'm not so sure this is an issue. I have Bitcoin Core and Namecoin both running. They use under 400MB each on a 8GB system, and don't impact anything else noticeably.
Hrm. I was noticing high CPU usage, so it's possible that was an issue. I ran disk defrag a month or two ago and it only reported 1% of fragmentation, which doesn't seem like that much. That said, it didn't tell me which 1% of the hard drive was fragmented. If that 2 GB or so was right smack in the middle of the blockchain, that'd cause some significant problems I'd imagine.
Granted, I do have an old fashioned hard drive, not an SSD. I'm seriously thinking of upgrading and am wondering whether bumping up my RAM or adding in an SSD would be better off performance wise. Any thoughts there?
There is such a thing as a hybrid SSD HDD. I don't really know anything about it (so you should look into it yourself), but it seems to allow you to boot quickly from SSD while performing most of your everyday tasks on the cheaper hard drive.
I wonder why there isn't more effort put in the direction of implementing QoS mechanisms (like throttling blockchain downloads) in the protocol. After all, the network as a whole does not become more efficient when single nodes hog down other nodes due to misconfigured blockchain downloading.
Downloading the blockchain is easy. A much bigger resource hog is verifying the blockchain.