htools - Cluster allocation and placement tools for Ganeti


cluster balancer
cluster checker
cluster capacity computation
IAllocator plugin
saves cluster state for later reuse
cluster information printer
cluster rolling maintenance scheduler


htools is a suite of tools designed to help with allocation/movement of instances and balancing of Ganeti clusters. htools is also the generic binary that must be symlinked or hardlinked under each tool’s name in order to perform the different functions. Alternatively, the environment variable HTOOLS can be used to set the desired role.

Installed as hbal, it computes and optionally executes a suite of instance moves in order to balance the cluster.

Installed as hcheck, it preforms cluster checks and optionally simulates rebalancing with all the hbal options available.

Installed as hspace, it computes how many additional instances can be fit on a cluster, while maintaining N+1 status. It can run on models of existing clusters or of simulated clusters.

Installed as hail, it acts as an IAllocator plugin, i.e. it is used by Ganeti to compute new instance allocations and instance moves.

Installed as hscan, it scans the local or remote cluster state and saves it to files which can later be reused by the other roles.

Installed as hinfo, it prints information about the current cluster state.

Installed as hroller, it helps scheduling maintenances that require node reboots on a cluster.


Options behave the same in all program modes, but not all program modes support all options. Some common options are:

-p, –print-nodes

Prints the node status, in a format designed to allow the user to understand the node’s most important parameters. If the command in question makes a cluster transition (e.g. balancing or allocation), then usually both the initial and final node status is printed.

It is possible to customise the listed information by passing a comma-separated list of field names to this option (the field list is currently undocumented), or to extend the default field list by prefixing the additional field list with a plus sign. By default, the node list will contain the following information:

a character denoting the status of the node, with ‘-‘ meaning an offline node, ‘*’ meaning N+1 failure and blank meaning a good node
the node name
the total node memory
the memory used by the node itself
the memory used by instances
amount memory which seems to be in use but cannot be determined why or by which instance; usually this means that the hypervisor has some overhead or that there are other reporting errors
the free node memory
the reserved node memory, which is the amount of free memory needed for N+1 compliance
total disk
free disk
the number of physical cpus on the node
the number of virtual cpus allocated to primary instances
number of primary instances
number of secondary instances
percent of free memory
percent of free disk
ratio of virtual to physical cpus
the dynamic CPU load (if the information is available)
the dynamic memory load (if the information is available)
the dynamic disk load (if the information is available)
the dynamic net load (if the information is available)
-t datafile, –text-data=*datafile*

Backend specification: the name of the file holding node and instance information (if not collecting via RAPI or LUXI). This or one of the other backends must be selected. The option is described in the man page htools(1).

The file should contain text data, line-based, with single empty lines separating sections. The lines themselves are column-based, with the pipe symbol (|) acting as separator.

The first section contains group data, with the following columns:

  • group name
  • group uuid
  • allocation policy
  • tags (separated by comma)
  • networks (UUID’s, separated by comma)

The second sections contains node data, with the following columns:

  • node name
  • node total memory
  • memory used by the node
  • node free memory
  • node total disk
  • node free disk
  • node physical cores
  • offline/role field (Y for offline nodes, N for online non-master nodes, and M for the master node which is always online)
  • group UUID
  • node spindle count
  • node tags
  • exclusive storage value (Y if active, N otherwise)
  • node free spindles
  • virtual CPUs used by the node OS

The third section contains instance data, with the fields:

  • instance name
  • instance memory
  • instance disk size
  • instance vcpus
  • instance status (in Ganeti’s format, e.g. running or ERROR_down)
  • instance auto_balance flag (see man page gnt-instance(8))
  • instance primary node
  • instance secondary node(s), if any
  • instance disk type (e.g. plain or drbd)
  • instance tags
  • spindle use back-end parameter
  • actual disk spindles used by the instance (it can be - when exclusive storage is not active)

The fourth section contains the cluster tags, with one tag per line (no columns/no column processing).

The fifth section contains the ipolicies of the cluster and the node groups, in the following format (separated by |):

  • owner (empty if cluster, group name otherwise)
  • standard, min, max instance specs; min and max instance specs are separated between them by a semicolon, and can be specified multiple times (min;max;min;max...); each of the specs contains the following values separated by commas: - memory size - cpu count - disk size - disk count - NIC count
  • disk templates
  • vcpu ratio
  • spindle ratio
If given the program will query all MonDs to fetch data from the supported data collectors over the network.
–mond-data datafile
The name of the file holding the data provided by MonD, to override quering MonDs over the network. This is mostly used for debugging. The file must be in JSON format and present an array of JSON objects , one for every node, with two members. The first member named node is the name of the node and the second member named reports is an array of report objects. The report objects must be in the same format as produced by the monitoring agent.
If given, all dynamic utilisation information will be ignored by assuming it to be 0. This option will take precedence over any data passed by the -U option (available with hbal) or by the MonDs with the --mond and the --mond-data option.
-m cluster
Backend specification: collect data directly from the cluster given as an argument via RAPI. If the argument doesn’t contain a colon (:), then it is converted into a fully-built URL via prepending https:// and appending the default RAPI port, otherwise it is considered a fully-specified URL and used as-is.
-L [path]
Backend specification: collect data directly from the master daemon, which is to be contacted via LUXI (an internal Ganeti protocol). An optional path argument is interpreted as the path to the unix socket on which the master daemon listens; otherwise, the default path used by Ganeti (configured at build time) is used.
-I|–ialloc-src path
Backend specification: load data directly from an iallocator request (as produced by Ganeti when doing an iallocator call). The iallocator request is read from specified path.
–simulate description

Backend specification: instead of using actual data, build an empty cluster given a node description. The description parameter must be a comma-separated list of five elements, describing in order:

  • the allocation policy for this node group (preferred, allocable or unallocable, or alternatively the short forms p, a or u)
  • the number of nodes in the cluster
  • the disk size of the nodes (default in mebibytes, units can be used)
  • the memory size of the nodes (default in mebibytes, units can be used)
  • the cpu core count for the nodes
  • the spindle count for the nodes

An example description would be preferred,20,100G,16g,4,2 describing a 20-node cluster where each node has 100GB of disk space, 16GiB of memory, 4 CPU cores and 2 disk spindles. Note that all nodes must have the same specs currently.

This option can be given multiple times, and each new use defines a new node group. Hence different node groups can have different allocation policies and node count/specifications.

-v, –verbose
Increase the output verbosity. Each usage of this option will increase the verbosity (currently more than 2 doesn’t make sense) from the default of one.
-q, –quiet
Decrease the output verbosity. Each usage of this option will decrease the verbosity (less than zero doesn’t make sense) from the default of one.
-V, –version
Just show the program version and exit.


Some options accept not simply numerical values, but numerical values together with a unit. By default, such unit-accepting options use mebibytes. Using the lower-case letters of m, g and t (or their longer equivalents of mib, gib, tib, for which case doesn’t matter) explicit binary units can be selected. Units in the SI system can be selected using the upper-case letters of M, G and T (or their longer equivalents of MB, GB, TB, for which case doesn’t matter).

More details about the difference between the SI and binary systems can be read in the units(7) man page.


The environment variable HTOOLS can be used instead of renaming/symlinking the programs; simply set it to the desired role and then the name of the program is no longer used.

Table Of Contents

Previous topic


Next topic


This Page