"[...] ARM servers are a big part of the future [...]"
Has anyone actually compared x86 and ARM doing some sort of comparable task, and measured how much power they both consume performing the same task? I know ARM uses a lot less power than x86, but if it uses 10 times as little power but takes 20 times as long to do the same task as an x86 server chip, it still uses more power. I'm not saying it isn't more power efficient than x86 (it certainly has that potential, because of all the old cruft in x86), but I just haven't seen any evidence that supports this claim.
Or am I missing the point? Is power efficiency not the main reason for ARM servers?
In many server applications your not CPU bound but rather IO bound. In those applications using the lowest power CPU makes sense. These are the applications ARM seems to be targeting first. Examples: $5 month static + php only website hosting market, front end load balancing, static file serving, etc.
The other possible target is embarrassingly parallel work loads where you really just want to cram as many cores into a given space as possible. Usually the limit of how many cores you can put in a rack is either power or cooling, not space.
Where you probably won't see ARM in the near term is on work loads that are highly single threaded and performance critical. I think this is exactly the type of situation your describing.
See Google's paper 'Brawny cores still beat wimpy cores, most of the time'. It concludes that 'Slower but energy efficient “wimpy” cores only win for general workloads if
their single-core speed is reasonably close to that of mid-range “brawny” cores.'
ARM boards are generally more power efficient for any given compute unit you want to benchmark, but it's not a huge advantage
And note that there are Intel solutions in the "cheap, low power" market too. There are ~$80 Cedar Trail boards (I forget the part numbers off-hand) which take 2GB of DDR3 memory and run on 15W or so at full CPU utilization.
The Ubuntu team was talking at SELF a few years back about using ARM clusters as web servers because of the low cost, high efficiency, and high core density you can achieve with the low-heat ARM chips.
Has anyone actually compared x86 and ARM doing some sort of comparable task, and measured how much power they both consume performing the same task? I know ARM uses a lot less power than x86, but if it uses 10 times as little power but takes 20 times as long to do the same task as an x86 server chip, it still uses more power. I'm not saying it isn't more power efficient than x86 (it certainly has that potential, because of all the old cruft in x86), but I just haven't seen any evidence that supports this claim.
Or am I missing the point? Is power efficiency not the main reason for ARM servers?