Something has been bugging me about the market share numbers
for server virtualization. Is the trend is just getting started, or is it
almost finished? The numbers I’ve seen say that under 10% of all X86 servers
have been virtualized – maybe 7-8%. By that measure, the trend of converting
physical servers into virtual ones seems to be quite early.
Things look very different when I look at the percentage of total servers (physical plus virtual)
that are virtual. Most customers seem to run at least 8-12 virtual servers per
physical, and some are pushing past 30 towards 50. Let’s use 10 as a
conservative number, and do the math: For every 100 physical servers, 7 are
virtualized, for a total of 70 virtual servers. That makes a total of 163 total
servers (70 + 93), and almost half are virtual. If we are half-way converted, then
the virtualization trend must be very far along, because the second half will
probably convert much faster than the first half.
It sure seems to me that looking at total servers is the
right thing to do, as opposed to just counting how many physical servers are
virtualized, because to a user, it shouldn’t make any difference whether their
server is virtual of physical. (That’s the whole point!)
On the other hand, it doesn’t feel right that server
virtualization is so far along. Most customers I talk with are just getting
started. Only a few have seriously converted. My math must be busted, because there’s
no way that we are half-way converted.
I think the problem is that the math assumes that there is a
fixed-size pool of servers that people are converting from physical to virtual.
It seems more likely that cheap and easy-to-provision virtual servers will lead
to a massive increase in the total number of servers. That is always what has
happened when a computing resource gets much less expensive. We didn’t just
replace workstations with PCs, we gave PCs to everyone, instead of just development engineers. Likewise, the cost
per gigabyte keeps dropping every year, but instead of buying fewer gigs, people
keep storing more and more, and their budgets stay roughly flat.
Given the history of the computer industry, it seems
unlikely that server virtualization will drive costs down in the way people think.
Instead, it seems much more likely that costs will stay roughly flat, but there
will be a radical proliferation in the number of virtual servers. They are just
so fast, easy and cheap to deploy, it seems likely that most IT shops will hand
out scads of them.
I’m not sure whether to think of this as a prediction, or a
warning. I guess if you get value from all those virtual servers (just like we
did from mini-computers, workstations, and then PCs), then there’s no problem.
But if IT shops really want to use server virtualization to save money, then they
had better be extraordinarily disciplined.