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I have a few questions, since the recent Amazon Cloudburst.

  1. Is it true, that attaching EBS as an external volume gives a better I/O performance than using EBS as a root device?
  2. How does IO take place between an instance and EBS volume mounted as
    1. Root Device.
    2. External volume. (Is it via the ethernet or on the same XEN server, or any other)

Since I am charged I/O on an external EBS, am I correct in guessing that the EBS volumes are in a different location than the instances?

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up vote 1 down vote accepted

EBS volumes are stored on completely different hardware than EC2 nodes are. As such, all IO to and from those volumes goes over the same network. When you hear people talking about faster IO being possible on attached volumes, they are referring to the usage of multiple EBS volumes in a RAID set.

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Also, don't get confused by people referring to the 'local disks' which are actually local hard drives, these go by the term Instance Store. Their performance can vary, but on different factors. – Flashman May 3 '11 at 21:28

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