A good article describing the evolution of GFS

It has been almost a decade since the GFS paper has been published. Since then, there are many changes that have been made. This interview here summarizes a few of them and the circumstances in which they are made

http://delivery.acm.org/10.1145/1600000/1594206/p10-case_study.pdf?ip=134.84.46.146&acc=OPEN&CFID=132372171&CFTOKEN=23979261&__acm__=1351194189_d2b32e9f2b0897f11d07caa688ed10c0