SYNOPSIS
--------
-**hail** [ **-t** *file* | **--simulate** *spec* ] [options...] *input-file*
+**hail** [ **-t** *file* | **\--simulate** *spec* ] [options...] *input-file*
-**hail** --version
+**hail** \--version
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
response. In case of critical failures, the error message is printed
on stderr and the exit code is changed to show failure.
+If the input file name is ``-`` (a single minus sign), then the request
+data will be read from *stdin*.
+
ALGORITHM
~~~~~~~~~
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.
+-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 **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.
+-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
+ 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).
+\--simulate *description*
+ 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
The exist status of the command will be zero, unless for some reason
the algorithm fatally failed (e.g. wrong node or instance data).
+BUGS
+----
+
+Networks (as configured by **gnt-network**\(8)) are not taken into
+account in Ganeti 2.7. The only way to guarantee that they work
+correctly is having your networks connected to all nodegroups. This will
+be fixed in a future version.
+
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projects / ganeti-local / blobdiff