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For OpenStack Autopilot, it was mentioned that

You’ll need at least five machines with two disks in each, two of which have two network interfaces (NICs)

So my question is MUST I have two disks on the servers? If yes then why?

Also do all machines have to be identical? like have same CPU model, same disks model, same RAM amount? Also can I have certain machines for storage, certain machines for compute and et cetera?

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Yes you must.

The architecture that Autopilot 15.11 uses to deploy OpenStack is fully converged. We deploy storage everywhere, for both block and object, alongside compute and networking. You can find out more about why in this talk from Tokyo's developer summit

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  • Ok thanks...my other question = Must i have identical machines? Can i use came CPU model, storage capacity, RAM capacity across all servers? Thanks again
    – uberrebu
    Jan 22, 2016 at 20:16
  • No they don't have to be identical. You can if that is easier for you, but any set of hardware (preferably ubuntu.com/certification/server certified but by no means required)
    – Adam Collard
    Jan 22, 2016 at 21:22
  • i will be using HP SL6500 with SL390s G7 server nodes youtube.com/watch?v=m2FQq_3BmDA
    – uberrebu
    Jan 22, 2016 at 21:57
  • What about the storage?;how does it pool storage? Does it RAID the storage or if i have 16 x 3TB HDD(2 each for 8 servers) how much storage s[ace does Openstack Autopilot give me? Also if all resources are pooled, does this mean it will average out the performance across all hard drives as well just like a SAN? Thanks
    – uberrebu
    Feb 3, 2016 at 4:52
  • Autopilot does not use RAID, with Ceph it is not necessary and not recommended, data resiliency comes from replication within the cluster. The Autopilot refarch uses one drive for the software running the system, the other is reserved for storage use.
    – 0xF2
    Mar 29, 2016 at 3:37
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Why does Ceph require two disks?

In the words of Mark Shuttleworth:

Ceph wants to keep track of the whole disk, literally, with the ability to format it and determine labels etc. This is so you can rip the disk out of one machine, stick it in another, and Ceph will see it, remember it, find all the data on it, as if nothing had changed.

source

Is it possible to do it on one disk?

Ceph can be configured to use a directory as opposed to the whole drive. However this is not recommended and, for that reason, not supported in autopilot.

Thanks to 0xF2 for the explanation.

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    Is it possible to have Ceph use a directory of the disk as opposed to the whole drive? Yes. Should you do this? No. Can the Autopilot deploy this definitely-not-recommended configuration? No.
    – 0xF2
    Mar 29, 2016 at 3:34

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