A few more "Rules of Thumb" highlights

More tidbits from Rules of Thumb in Data Engineering:

• In ten years RAM will cost what disk does today.
• A (full-time) person can administer a million dollars worth of disk storage (if I got the math right, that's about 3PB these days -- it was 30TB in 1999)
• In 1999, a CPU could keep 40-50 disks busy (and for some applications it should be doing just that). The number is probably not changing very quickly.
  
• At the time the article was written, two ratios appeared to be dropping rapidly. If the predictions held true (I haven't checked yet), the impact could be significant:
• The CPU cost of network access vs. disk access, measured both per message and per byte.
• The dollar cost per byte transferred of WAN vs. LAN
  
• You should pretty much always cache a web page.