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Ganeti 2.0 design documents

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The 2.x versions of Ganeti will constitute a rewrite of the 'core'

architecture, plus some additional features (however 2.0 is geared

toward the core changes).

Core changes

------------

The main changes will be switching from a per-process model to a

daemon based model, where the individual gnt-* commands will be

clients that talk to this daemon (see the design-2.0-master-daemon

document). This will allow us to get rid of the global cluster lock

for most operations, having instead a per-object lock (see

design-2.0-granular-locking). Also, the daemon will be able to queue

jobs, and this will allow the invidual clients to submit jobs without

waiting for them to finish, and also see the result of old requests

(see design-2.0-job-queue).

Beside these major changes, another 'core' change but that will not be

as visible to the users will be changing the model of object attribute

storage, and separate that into namespaces (such that an Xen PVM

instance will not have the Xen HVM parameters). This will allow future

flexibility in defining additional parameters. More details in the

design-2.0-cluster-parameters document.

The various changes brought in by the master daemon model and the

read-write RAPI will require changes to the cluster security; we move

away from Twisted and use http(s) for intra- and extra-cluster

communications. For more details, see the security document in the

doc/ directory.

Functionality changes

---------------------

The disk storage will receive some changes, and will also remove

support for the drbd7 and md disk types. See the

design-2.0-disk-changes document.

The configuration storage will be changed, with the effect that more

data will be available on the nodes for access from outside ganeti

(e.g. from shell scripts) and that nodes will get slightly more

awareness of the cluster configuration.

The RAPI will enable modify operations (beside the read-only queries

that are available today), so in effect almost all the operations

available today via the ``gnt-*`` commands will be available via the

remote API.

A change in the hypervisor support area will be that we will support

multiple hypervisors in parallel in the same cluster, so one could run

Xen HVM side-by-side with Xen PVM on the same cluster.

New features

------------

There will be a number of minor feature enhancements targeted to

either 2.0 or subsequent 2.x releases:

- multiple disks, with custom properties (read-only/read-write, exportable,

  etc.)

- multiple NICs

These changes will require OS API changes, details are in the

design-2.0-os-interface document. And they will also require many

command line changes, see the design-2.0-commandline-parameters

document.