DESCRIPTION
-----------
-hail is a Ganeti IAllocator plugin that allows automatic instance
-placement and automatic instance secondary node replacement using the
-same algorithm as **hbal**(1).
+hail is a Ganeti IAllocator plugin that implements the instance
+placement and movement using the same algorithm as **hbal**(1).
The program takes input via a JSON-file containing current cluster
state and the request details, and output (on stdout) a JSON-formatted
The program uses a simplified version of the hbal algorithm.
-For relocations, we try to change the secondary node of the instance
-to all the valid other nodes; the node which results in the best
-cluster score is chosen.
-
For single-node allocations (non-mirrored instances), again we
select the node which, when chosen as the primary node, gives the best
score.
pair; this is the only choice where the algorithm is non-trivial
with regard to cluster size.
-For node evacuations (*multi-evacuate* mode), we iterate over all
-instances which live as secondaries on those nodes and try to relocate
-them using the single-instance relocation algorithm.
+For relocations, we try to change the secondary node of the instance to
+all the valid other nodes; the node which results in the best cluster
+score is chosen.
+
+For node changes (*change-node* mode), we currently support DRBD
+instances only, and all three modes (primary changes, secondary changes
+and all node changes).
+
+For group moves (*change-group* mode), again only DRBD is supported, and
+we compute the correct sequence that will result in a group change; job
+failure mid-way will result in a split instance. The choice of node(s)
+on the target group is based on the group score, and the choice of group
+is based on the same algorithm as allocations (group with lowest score
+after placement).
+
+The deprecated *multi-evacuate* modes is no longer supported.
-In all cases, the cluster scoring is identical to the hbal algorithm.
+In all cases, the cluster (or group) scoring is identical to the hbal
+algorithm.
OPTIONS
-------
The options that can be passed to the program are as follows:
-p, --print-nodes
- Prints the before and after node status, in a format designed to
- allow the user to understand the node's most important
- parameters. See the man page **hbal**(1) for more details about this
- field.
+ Prints the before and after node status, in a format designed to allow
+ the user to understand the node's most important parameters. See the
+ man page **htools**(1) for more details about this option.
-t *datafile*, --text-data=*datafile*
- The name of the file holding cluster information, to override the
- data in the JSON request itself. This is mostly used for debugging.
+ The name of the file holding cluster information, to override the data
+ in the JSON request itself. This is mostly used for debugging. The
+ format of the file is described in the man page **htools**(1).
--simulate *description*
- Similar to the **-t** option, this allows overriding the cluster
- data with a simulated cluster. For details about the description,
- see the man page **hspace**(1).
+ Backend specification: similar to the **-t** option, this allows
+ overriding the cluster data with a simulated cluster. For details
+ about the description, see the man page **htools**(1).
+
+-S *filename*, --save-cluster=*filename*
+ If given, the state of the cluster before and the iallocator run is
+ saved to a file named *filename.pre-ialloc*, respectively
+ *filename.post-ialloc*. This allows re-feeding the cluster state to
+ any of the htools utilities via the ``-t`` option.
-v
This option increases verbosity and can be used for debugging in order