ARM is 32bit for now which limits its utility serving large databases. ARM is virtualizing its 32bit address space to permit extending use of the processor to servers better. ARM should be able to compete very well in service/watt with x86 and a number of projects are on the go to extend this Year of ARM to the server. One has already come to market.
Isn’t competition grand? Instead of having only a choice of AMD/Intel and multiple core x86-64 chips we can think smaller and more flexibly with potential for more transactions/watt.