[Pacemaker] difference between anonymous and globally unique clone

[Andrew Beekhof]

2009/3/30 Glory Smith <xx2glory at gmail.com>:
> Hi All,
> can any one help me in understanding the difference between anonymous and
> globally unique clone.  anonymous Clones are supposed to behave identically
> everywhere they are running but globally unique clone can behave differently
> .

Right.

The best way to think about it is "Does the resource agent do anything
based on the clone number?" (The clone number is the bit after the
colon in the resource's name.  eg. nfs-client:1).
If yes, then your clone _must_ be of the "globally unique" type.

Common reasons for needing to answer "yes" to the question above:
- The ability to run more than one instance per node
- Using the clone number as part of a hash function to perform load
balancing (eg. a cloned IP address)

Its worth mentioning that all clones of LSB resources are anonymous,
because there can only be one copy active per node (specifically the
status function wont function correctly for more than one copy).
I believe drbd is another one that must be anonymous since the kernel
module can only be loaded once per node.

> my understanding is, every resource agent has some sets of functions like
> start, stop ,monitor. as it will be just executing start, stop according to
> the resource's action . so if i do start on anonymous clone then it will be
> started on all nodes. but  in case of globally unique i can start , stop
> clone's resources on  individual node . is my understanding right?

No.
Neither type of resource allows you to place a specific instance on a
particular node, this is by design.

The difference is that anonymous clones only allow you to have one
instance per node.
Internally, this allows the PE to make certain assumptions when
managing the resource.

> does it have any other difference also?.
>
> Best Regards,
>
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