Back in the late 1980's and early 1990's, I was one of the architects for DFSMS on z/OS, and customers always asked, "What is the clip level?", in other words, how big does a customer have to be to take advantage of DFSMS. We worked it out that if you had more than 100GB of disk data, DFSMS is worthwhile. DFSMS is now just standard by default, as everyone now easily has more than 100GB of data.
Later, in the late 1990's, I worked on Linux for System z. Again, customers asked how many Linux guest images would justify deploying applications on a mainframe. We worked it out to about 10 images. 10 Linux logical partitions, or Linux guests under z/VM was enough to cost justify the entire investment.
So what is the "clip level" for SANs? How many servers does an SMB need to have to justify deploying a SAN? IBM announced the new BladeCenter S designed specifically for mid-sized companies, 100 to 1000 employees, typically running 25 to 45 servers. However, I suspect companies as small as 7-10 servers would probably benefit from deploying an FC or IP SAN.
What do you think? Send me a comment on how many servers should be the clip level.