You're looking at two different things. The number of cores is one thing, and the power of each core another. Number of cores is pretty straight forward, and the power is relative to that of a small instance. You've got the answer right there in your email- there are two virtual cores of two compute units each, so you will only see two cores. Those cores are twice as powerful as the typical core (hence the two compute units), but they are still only going to show two cores.
This does have a bit of an effect on processing jobs. If you need more CPU power behind your tasks than a large instance will be nice, but if your bottleneck is something else (memory, disk i/o, s3 access, etc) then you'll probably be optimizing for the wrong problem. In my experience it's better to have four small instances running in a job than one large instance, even though the cost is equivalent. If you're using spot instances- which are a huge budget saver- then the small instances make even more sense, since lost machines will only result in one lost task instead of four. Robert On Nov 24, 2011, at 7:40 AM , Jiamin Lu wrote: > Hi, all > > I am using the Amazon EC2, with their large instances. > Amazon claims these large type instances have 4 EC2 Compute units (2 virtual > cores with 2 EC2 Compute Units each). > But according to my observation, it seems like they only have two cores. > > I checked the /proc/cpuinfo, which shows there are only two processors, > I also used the top command, and it also says only two cpu there. > > Can someone tell me actually how many cores are contained inside these large > instances? > Did I misunderstand these terms that Amazon talks about ?? > > Thanks > > Jiamin Lu >
