A question about Amazon EC2 Compute Units

I have a large EC2 server instance on Amazon.开发者_JAVA百科 Reading on wikipedia shows the following details of a Large Instance.

7.5 GB memory
4 EC2 Compute Units (2 virtual cores with 2 EC2 Compute Units each)
850 GB instance storage (2×420 GB plus 10 GB root partition)
64-bit platform
I/O Performance: High
API name: m1.large

Q: What exactly is a compute unit? I know I shouldn't be multiplying 2 cores with 2 compute units to get 4 cores because running htop on the machine only shows 2 cores. Same with cat /proc/cpuinfo.

Q:I do not see 850 G of storage anywhere on the instance. How do I utilize that?

THanks

1. From the AWS documentation:

Amazon EC2 uses a variety of measures to provide each instance with a consistent and predictable amount of CPU capacity. In order to make it easy for developers to compare CPU capacity between different instance types, we have defined an Amazon EC2 Compute Unit. The amount of CPU that is allocated to a particular instance is expressed in terms of these EC2 Compute Units. We use several benchmarks and tests to manage the consistency and predictability of the performance of an EC2 Compute Unit. One EC2 Compute Unit provides the equivalent CPU capacity of a 1.0-1.2 GHz 2007 Opteron or 2007 Xeon processor. This is also the equivalent to an early-2006 1.7 GHz Xeon processor referenced in our original documentation. Over time, we may add or substitute measures that go into the definition of an EC2 Compute Unit, if we find metrics that will give you a clearer picture of compute capacity.

1. Just type "df -h" (or look at your computer properties if you're on Windows) and you should see a breakdown of the instance's file systems and sizes.

I would use the AWS docs rather than Wikipedia as the source of truth for exactly what each instance type gives you.

I do not see 850 G of storage anywhere on the instance. How do I utilize that?

The instance storage is not formatted by default, so to utilize it you first need to create a file system on it, format it, and mount it.

This is 850G ephemeral or instance storage. Take look at the Instance Storage docs. The new AMIs do not have that storage attached, but you can create custom AMI (see the example) or create the instance programmatically.

The storage was formatted last time I used it, but you can easily do that and then mount/attach it wherever you want.