There is a bug in BetterStorage that causes a high usage loop to be entered if any chunk loads with any of the better storage items actively in use (reinforced chests, Armor stands, leather backpacks (not the ones for the backpacks mod), etc). I worked with copyboy and we found the issue. It is fixed in the 0.6.2.23-hotfix version he just put out. If you have these items in use, the server will spend about 25% of every tick cycle doing better storage stuff causing the server to lag like crazy. The more of the items you have, the more obvious it is and it can slowly creep up on you as you add chests and stuff until you suddenly realize your server is slow and nothing you do seems to help. Doing a restart only helps for a little while and then things go downhill as soon as some chunks with those items get loaded in.
Now we just need to get that hotfix into Hexxit so it can be updated and people can use these items.