Move large (100GB) file to EC2 instance from the colo data center

Just to add a little to the consensus that is EBS faster...

An important point to understand here is that instance storage speed is unpredictable - Amazon makes no guarantees about it.

This information comes from the book Cloud Application Architectures by George Reese (which seems pretty good from what I've skimmed it so far.) It includes a table titled Comparison of EC2 data storage options (p. 41); here's a snippet of that table (in the book there are several other characteristics compared):

               S3              Instance          EBS

Speed          Low             Unpredictable     High
Reliability    Medium          High              High
Durability     Super high      Super low         High

So, instance storage might outperform EBS in read access sometimes, but if you want constant high speed, you indeed need to go with EBS. As Reese puts it in his book:

Another issue is the unpredictability of performance in the instance storage. You might actually think that it should be faster than the other options, and sometimes it is. Sometimes, however, it is unbelievably slow - slower than an NFS mount over a 10bT Ethernet connection. EBS, on the other hand, consistently gives you the performance of a SAN over a GB Ethernet connection.

The host key is generated on first boot of any instance. Init scripts are run at every boot that access the machine instance data. The initscript saves the instance id in a particular file: this way, if the file is absent or contains a different ID, the system initialization stuff is run.

That includes generating the host key (stored at /etc/ssh/ssh_host_{rsa,dsa}_key), downloading the user public key from the metadata and storing it in the authorized_keys file, setting the hostname, and performing any other system-specific initialization.

Since the determining factor is not the hard disk, but the (unique to each instance) instance ID, these things will always be done when you boot EBS volume attached to a new instance.

Edit:

I looked deeper into Ubuntu specifically and installed an ubuntu ami (3ffb3f56). I'm not a big ubuntu guy (usually prefer debian) so this was getting a little deeper into the ubuntu upstart-based init sequence than I usually go. It seems what you're looking at are /etc/init/cloud*.conf. These run /usr/bin/cloud-init and friends, which have lines like

cloud.sem_and_run("set_defaults", "once-per-instance",
        set_defaults,[ cloud ],False)

All the code's in python, so it's pretty readable. The base is provided by the package cloud-init and the backend for the scripts is provided by cloud-tools. You could look and see how it determines "once-per-instance" and trick it that way, or work around your problem with some other solution. Best of luck!