hspace computes how many additional instances can be fit on a cluster,
while maintaining N+1 status.
The program will try to place instances, all of the same size, on the
cluster, until the point where we don't have any N+1 possible
allocation. It uses the exact same allocation algorithm as the hail
The output of the program is designed to interpreted as a shell
fragment (or parsed as a key=value file). Options which extend
the output (e.g. -p, -v) will output the additional information on
stderr (such that the stdout is still parseable).
The following keys are available in the output of the script (all
prefixed with HTS_):
SPEC_MEM, SPEC_DSK, SPEC_CPU, SPEC_RQN
These represent the specifications of the instance model used for
allocation (the memory, disk, cpu, requested nodes).
These represent the total memory, disk, CPU count and total nodes in
These are the initial (current) and final cluster score (see the hbal
man page for details about the scoring algorithm).
The initial and final instance count.
The initial and final total free memory in the cluster (but this
doesn't necessarily mean available for use).
The initial and final total available memory for allocation in the
cluster. If allocating redundant instances, new instances could
increase the reserved memory so it doesn't necessarily mean the
entirety of this memory can be used for new instance allocations.
The initial and final reserved memory (for redundancy/N+1 purposes).
The initial and final memory used for instances (actual runtime used
The initial and final memory overhead --- memory used for the node
itself and unacounted memory (e.g. due to hypervisor overhead).
The initial and final memory efficiency, represented as instance
memory divided by total memory.
Initial and final number of virtual CPUs used by instances.
The initial and final CPU efficiency, represented as the count of
virtual instance CPUs divided by the total physical CPU count.
The initial and final maximum per-node available memory. This is not
very useful as a metric but can give an impression of the status of
the nodes; as an example, this value restricts the maximum instance
size that can be still created on the cluster.
Like the above but for disk.
If the tiered allocation mode has been enabled, this parameter holds
the pairs of specifications and counts of instances that can be
created in this mode. The value of the key is a space-separated list
of values; each value is of the form memory,disk,vcpu=count
where the memory, disk and vcpu are the values for the current spec,
and count is how many instances of this spec can be created. A
complete value for this variable could be: 4096,102400,2=225
KM_USED_CPU, KM_USED_MEM, KM_USED_DSK
These represents the metrics of used resources at the start of the
computation (only for tiered allocation mode).
KM_POOL_CPU, KM_POOL_MEM, KM_POOL_DSK
These represents the total resources allocated during the tiered
allocation process. In effect, they represent how much is readily
available for allocation.
KM_UNAV_CPU, KM_UNAV_MEM, KM_UNAV_DSK
These represents the resources left over (either free as in
unallocable or allocable on their own) after the tiered allocation has
been completed. They represent better the actual unallocable
resources, because some other resource has been exhausted. For
example, the cluster might still have 100GiB disk free, but with no
memory left for instances, we cannot allocate another instance, so in
effect the disk space is unallocable. Note that the CPUs here
represent instance virtual CPUs, and in case the --max-cpu
option hasn't been specified this will be -1.
The current usage represented as initial number of instances divided
per final number of instances.
The number of instances allocated (delta between FIN_INST_CNT and
For the last attemp at allocations (which would have increased
FIN_INST_CNT with one, if it had succeeded), this is the count of the
failure reasons per failure type; currently defined are FAILMEM,
FAILDISK and FAILCPU which represent errors due to not enough memory,
disk and CPUs, and FAILN1 which represents a non N+1 compliant cluster
on which we can't allocate instances at all.
The reason for most of the failures, being one of the above FAIL*
A marker representing the successful end of the computation, and
having value "1". If this key is not present in the output it means
that the computation failed and any values present should not be
If the tiered allocation mode is enabled, then many of the INI_/FIN_
metrics will be also displayed with a TRL_ prefix, and denote the
cluster status at the end of the tiered allocation run.
The options that can be passed to the program are as follows:
The memory size of the instances to be placed (defaults to 4GiB).
The disk size of the instances to be placed (defaults to 100GiB).
The number of nodes for the instances; the default of two means
mirrored instances, while passing one means plain type instances.
The number of VCPUs of the instances to be placed (defaults to 1).
The maximum virtual-to-physical cpu ratio, as a floating point
number between zero and one. For example, specifying cpu-ratio
as 2.5 means that, for a 4-cpu machine, a maximum of 10
virtual cpus should be allowed to be in use for primary instances. A
value of one doesn't make sense though, as that means no disk space
can be used on it.
The minimum amount of free disk space remaining, as a floating point
number. For example, specifying disk-ratio as 0.25 means
that at least one quarter of disk space should be left free on nodes.
Prints the before and after node status, in a format designed to allow
the user to understand the node's most important parameters.
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
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)
This option (which can be given multiple times) will mark nodes as
being offline, and instances won't be placed on these nodes.
Note that hspace will also mark as offline any nodes which are
reported by RAPI as such, or that have "?" in file-based input in any
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
Collect data directly from the
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's
considered a fully-specified URL and is used as-is.
Collect data directly from the master daemon, which is to be contacted
via the 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 when
installed with --localstatedir=/var is used.
Instead of using actual data, build an empty cluster given a node
description. The description parameter must be a
comma-separated list of four elements, describing in order:
the number of nodes in the cluster
the disk size of the nodes, in mebibytes
the memory size of the nodes, in mebibytes
the cpu core count for the nodes
An example description would be 20,102400,16384,4 describing a
20-node cluster where each node has 100GiB of disk space, 16GiB of
memory and 4 CPU cores. Note that all nodes must have the same specs
Beside the standard, fixed-size allocation, also do a tiered
allocation scheme where the algorithm starts from the given
specification and allocates until there is no more space; then it
decreases the specification and tries the allocation again. The
decrease is done on the matric that last failed during allocation. The
specification given is similar to the --simulate option and it
the disk size of the instance
the memory size of the instance
the vcpu count for the insance
An example description would be 10240,8192,2 describing an
initial starting specification of 10GiB of disk space, 4GiB of memory
and 2 VCPUs.
Also note that the normal allocation and the tiered allocation are
independent, and both start from the initial cluster state; as such,
the instance count for these two modes are not related one to another.
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. At verbosity 2 the location of the new instances is
shown in the standard error.
Decrease the output verbosity. Each usage of this option will decrease
the verbosity (less than zero doesn't make sense) from the default of
Just show the program version and exit.
The exist status of the command will be zero, unless for some reason
the algorithm fatally failed (e.g. wrong node or instance data).
The algorithm is highly dependent on the number of nodes; its runtime
grows exponentially with this number, and as such is impractical for
really big clusters.
The algorithm doesn't rebalance the cluster or try to get the optimal
fit; it just allocates in the best place for the current step, without
taking into consideration the impact on future placements.
If the variables HTOOLS_NODES and HTOOLS_INSTANCES are
present in the environment, they will override the default names for
the nodes and instances files. These will have of course no effect
when the RAPI or Luxi backends are used.
Copyright (C) 2009 Google Inc. Permission is granted to copy,
distribute and/or modify under the terms of the GNU General Public
License as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
On Debian systems, the complete text of the GNU General Public License
can be found in /usr/share/common-licenses/GPL.