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HSPACE(1) Ganeti | Version @GANETI_VERSION@
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===========================================
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NAME
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----
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hspace - Cluster space analyzer for Ganeti
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SYNOPSIS
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--------
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**hspace** {backend options...} [algorithm options...] [request options...]
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[output options...] [-v... | -q]
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**hspace** --version
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Backend options:
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{ **-m** *cluster* | **-L[** *path* **] [-X]** | **-t** *data-file* |
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**--simulate** *spec* }
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Algorithm options:
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**[ --max-cpu *cpu-ratio* ]**
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**[ --min-disk *disk-ratio* ]**
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**[ -O *name...* ]**
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Request options:
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**[--memory** *mem* **]**
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**[--disk** *disk* **]**
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**[--disk-template** *template* **]**
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**[--vcpus** *vcpus* **]**
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**[--tiered-alloc** *spec* **]**
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Output options:
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**[--machine-readable**[=*CHOICE*] **]**
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**[-p**[*fields*]**]**
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DESCRIPTION
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-----------
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hspace computes how many additional instances can be fit on a cluster,
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while maintaining N+1 status.
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The program will try to place instances, all of the same size, on the
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cluster, until the point where we don't have any N+1 possible
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allocation. It uses the exact same allocation algorithm as the hail
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iallocator plugin in *allocate* mode.
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The output of the program is designed either for human consumption (the
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default) or, when enabled with the ``--machine-readable`` option
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(described further below), for machine consumption. In the latter case,
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it is intended to interpreted as a shell fragment (or parsed as a
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*key=value* file). Options which extend the output (e.g. -p, -v) will
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output the additional information on stderr (such that the stdout is
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still parseable).
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The following keys are available in the machine-readable output of the
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script (all prefixed with *HTS_*):
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SPEC_MEM, SPEC_DSK, SPEC_CPU, SPEC_RQN, SPEC_DISK_TEMPLATE
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  These represent the specifications of the instance model used for
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  allocation (the memory, disk, cpu, requested nodes, disk template).
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TSPEC_INI_MEM, TSPEC_INI_DSK, TSPEC_INI_CPU, ...
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  Only defined when the tiered mode allocation is enabled, these are
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  similar to the above specifications but show the initial starting spec
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  for tiered allocation.
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CLUSTER_MEM, CLUSTER_DSK, CLUSTER_CPU, CLUSTER_NODES
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  These represent the total memory, disk, CPU count and total nodes in
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  the cluster.
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INI_SCORE, FIN_SCORE
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  These are the initial (current) and final cluster score (see the hbal
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  man page for details about the scoring algorithm).
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INI_INST_CNT, FIN_INST_CNT
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  The initial and final instance count.
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INI_MEM_FREE, FIN_MEM_FREE
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  The initial and final total free memory in the cluster (but this
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  doesn't necessarily mean available for use).
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INI_MEM_AVAIL, FIN_MEM_AVAIL
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  The initial and final total available memory for allocation in the
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  cluster. If allocating redundant instances, new instances could
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  increase the reserved memory so it doesn't necessarily mean the
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  entirety of this memory can be used for new instance allocations.
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INI_MEM_RESVD, FIN_MEM_RESVD
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  The initial and final reserved memory (for redundancy/N+1 purposes).
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INI_MEM_INST, FIN_MEM_INST
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  The initial and final memory used for instances (actual runtime used
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  RAM).
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INI_MEM_OVERHEAD, FIN_MEM_OVERHEAD
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  The initial and final memory overhead--memory used for the node
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  itself and unacounted memory (e.g. due to hypervisor overhead).
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INI_MEM_EFF, HTS_INI_MEM_EFF
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  The initial and final memory efficiency, represented as instance
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  memory divided by total memory.
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INI_DSK_FREE, INI_DSK_AVAIL, INI_DSK_RESVD, INI_DSK_INST, INI_DSK_EFF
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  Initial disk stats, similar to the memory ones.
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FIN_DSK_FREE, FIN_DSK_AVAIL, FIN_DSK_RESVD, FIN_DSK_INST, FIN_DSK_EFF
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  Final disk stats, similar to the memory ones.
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INI_CPU_INST, FIN_CPU_INST
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  Initial and final number of virtual CPUs used by instances.
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INI_CPU_EFF, FIN_CPU_EFF
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  The initial and final CPU efficiency, represented as the count of
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  virtual instance CPUs divided by the total physical CPU count.
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INI_MNODE_MEM_AVAIL, FIN_MNODE_MEM_AVAIL
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  The initial and final maximum per-node available memory. This is not
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  very useful as a metric but can give an impression of the status of
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  the nodes; as an example, this value restricts the maximum instance
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  size that can be still created on the cluster.
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INI_MNODE_DSK_AVAIL, FIN_MNODE_DSK_AVAIL
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  Like the above but for disk.
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TSPEC
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  If the tiered allocation mode has been enabled, this parameter holds
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  the pairs of specifications and counts of instances that can be
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  created in this mode. The value of the key is a space-separated list
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  of values; each value is of the form *memory,disk,vcpu=count* where
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  the memory, disk and vcpu are the values for the current spec, and
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  count is how many instances of this spec can be created. A complete
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  value for this variable could be: **4096,102400,2=225
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  2560,102400,2=20 512,102400,2=21**.
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KM_USED_CPU, KM_USED_NPU, KM_USED_MEM, KM_USED_DSK
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  These represents the metrics of used resources at the start of the
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  computation (only for tiered allocation mode). The NPU value is
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  "normalized" CPU count, i.e. the number of virtual CPUs divided by
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  the maximum ratio of the virtual to physical CPUs.
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KM_POOL_CPU, KM_POOL_NPU, KM_POOL_MEM, KM_POOL_DSK
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  These represents the total resources allocated during the tiered
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  allocation process. In effect, they represent how much is readily
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  available for allocation.
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KM_UNAV_CPU, KM_POOL_NPU, KM_UNAV_MEM, KM_UNAV_DSK
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  These represents the resources left over (either free as in
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  unallocable or allocable on their own) after the tiered allocation
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  has been completed. They represent better the actual unallocable
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  resources, because some other resource has been exhausted. For
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  example, the cluster might still have 100GiB disk free, but with no
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  memory left for instances, we cannot allocate another instance, so
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  in effect the disk space is unallocable. Note that the CPUs here
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  represent instance virtual CPUs, and in case the *--max-cpu* option
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  hasn't been specified this will be -1.
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ALLOC_USAGE
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  The current usage represented as initial number of instances divided
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  per final number of instances.
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ALLOC_COUNT
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  The number of instances allocated (delta between FIN_INST_CNT and
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  INI_INST_CNT).
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ALLOC_FAIL*_CNT
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  For the last attemp at allocations (which would have increased
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  FIN_INST_CNT with one, if it had succeeded), this is the count of
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  the failure reasons per failure type; currently defined are FAILMEM,
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  FAILDISK and FAILCPU which represent errors due to not enough
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  memory, disk and CPUs, and FAILN1 which represents a non N+1
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  compliant cluster on which we can't allocate instances at all.
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ALLOC_FAIL_REASON
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  The reason for most of the failures, being one of the above FAIL*
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  strings.
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OK
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  A marker representing the successful end of the computation, and
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  having value "1". If this key is not present in the output it means
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  that the computation failed and any values present should not be
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  relied upon.
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If the tiered allocation mode is enabled, then many of the INI_/FIN_
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metrics will be also displayed with a TRL_ prefix, and denote the
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cluster status at the end of the tiered allocation run.
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The human output format should be self-explanatory, so it is not
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described further.
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OPTIONS
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-------
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The options that can be passed to the program are as follows:
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--memory *mem*
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  The memory size of the instances to be placed (defaults to
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  4GiB). Units can be used (see below for more details).
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--disk *disk*
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  The disk size of the instances to be placed (defaults to
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  100GiB). Units can be used.
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--disk-template *template*
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  The disk template for the instance; one of the Ganeti disk templates
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  (e.g. plain, drbd, so on) should be passed in.
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--vcpus *vcpus*
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  The number of VCPUs of the instances to be placed (defaults to 1).
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--max-cpu=*cpu-ratio*
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  The maximum virtual to physical cpu ratio, as a floating point number
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  greater than or equal to one. For example, specifying *cpu-ratio* as
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  **2.5** means that, for a 4-cpu machine, a maximum of 10 virtual cpus
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  should be allowed to be in use for primary instances. A value of
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  exactly one means there will be no over-subscription of CPU (except
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  for the CPU time used by the node itself), and values below one do not
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  make sense, as that means other resources (e.g. disk) won't be fully
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  utilised due to CPU restrictions.
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--min-disk=*disk-ratio*
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  The minimum amount of free disk space remaining, as a floating point
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  number. For example, specifying *disk-ratio* as **0.25** means that
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  at least one quarter of disk space should be left free on nodes.
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-l *rounds*, --max-length=*rounds*
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  Restrict the number of instance allocations to this length. This is
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  not very useful in practice, but can be used for testing hspace
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  itself, or to limit the runtime for very big clusters.
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-p, --print-nodes
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  Prints the before and after node status, in a format designed to allow
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  the user to understand the node's most important parameters. See the
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  man page **htools**(1) for more details about this option.
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-O *name*
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  This option (which can be given multiple times) will mark nodes as
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  being *offline*. This means a couple of things:
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  - instances won't be placed on these nodes, not even temporarily;
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    e.g. the *replace primary* move is not available if the secondary
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    node is offline, since this move requires a failover.
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  - these nodes will not be included in the score calculation (except
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    for the percentage of instances on offline nodes)
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  Note that the algorithm will also mark as offline any nodes which
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  are reported by RAPI as such, or that have "?" in file-based input
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  in any numeric fields.
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-S *filename*, --save-cluster=*filename*
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  If given, the state of the cluster at the end of the allocation is
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  saved to a file named *filename.alloc*, and if tiered allocation is
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  enabled, the state after tiered allocation will be saved to
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  *filename.tiered*. This allows re-feeding the cluster state to
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  either hspace itself (with different parameters) or for example
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  hbal, via the ``-t`` option.
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-t *datafile*, --text-data=*datafile*
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  Backend specification: the name of the file holding node and instance
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  information (if not collecting via RAPI or LUXI). This or one of the
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  other backends must be selected. The option is described in the man
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  page **htools**(1).
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-m *cluster*
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  Backend specification: collect data directly from the *cluster* given
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  as an argument via RAPI. The option is described in the man page
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  **htools**(1).
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-L [*path*]
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  Backend specification: collect data directly from the master daemon,
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  which is to be contacted via LUXI (an internal Ganeti protocol). The
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  option is described in the man page **htools**(1).
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--simulate *description*
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  Backend specification: similar to the **-t** option, this allows
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  overriding the cluster data with a simulated cluster. For details
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  about the description, see the man page **htools**(1).
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--tiered-alloc *spec*
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  Besides the standard, fixed-size allocation, also do a tiered
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  allocation scheme where the algorithm starts from the given
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  specification and allocates until there is no more space; then it
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  decreases the specification and tries the allocation again. The
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  decrease is done on the matric that last failed during
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  allocation. The specification given is similar to the *--simulate*
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  option and it holds:
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  - the disk size of the instance (units can be used)
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  - the memory size of the instance (units can be used)
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  - the vcpu count for the insance
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  An example description would be *100G,4g,2* describing an initial
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  starting specification of 100GB of disk space, 4GiB of memory and 2
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  VCPUs.
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  Also note that the normal allocation and the tiered allocation are
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  independent, and both start from the initial cluster state; as such,
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  the instance count for these two modes are not related one to
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  another.
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--machines-readable[=*choice*]
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  By default, the output of the program is in "human-readable" format,
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  i.e. text descriptions. By passing this flag you can either enable
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  (``--machine-readable`` or ``--machine-readable=yes``) or explicitly
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  disable (``--machine-readable=no``) the machine readable format
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  described above.
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-v, --verbose
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  Increase the output verbosity. Each usage of this option will
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  increase the verbosity (currently more than 2 doesn't make sense)
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  from the default of one.
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-q, --quiet
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  Decrease the output verbosity. Each usage of this option will
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  decrease the verbosity (less than zero doesn't make sense) from the
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  default of one.
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-V, --version
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  Just show the program version and exit.
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UNITS
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~~~~~
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By default, all unit-accepting options use mebibytes. Using the
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lower-case letters of *m*, *g* and *t* (or their longer equivalents of
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*mib*, *gib*, *tib*, for which case doesn't matter) explicit binary
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units can be selected. Units in the SI system can be selected using the
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upper-case letters of *M*, *G* and *T* (or their longer equivalents of
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*MB*, *GB*, *TB*, for which case doesn't matter).
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More details about the difference between the SI and binary systems can
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be read in the *units(7)* man page.
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EXIT STATUS
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-----------
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The exist status of the command will be zero, unless for some reason
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the algorithm fatally failed (e.g. wrong node or instance data).
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BUGS
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----
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The algorithm is highly dependent on the number of nodes; its runtime
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grows exponentially with this number, and as such is impractical for
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really big clusters.
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The algorithm doesn't rebalance the cluster or try to get the optimal
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fit; it just allocates in the best place for the current step, without
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taking into consideration the impact on future placements.
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.. vim: set textwidth=72 :
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.. Local Variables:
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.. mode: rst
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.. fill-column: 72
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.. End: