Synnefo » snf-ganeti

HSPACE(1) Ganeti | Version @GANETI_VERSION@

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NAME

----

hspace - Cluster space analyzer for Ganeti

SYNOPSIS

--------

**hspace** {backend options...} [algorithm options...] [request options...]

[output options...] [-v... | -q]

**hspace** --version

Backend options:

{ **-m** *cluster* | **-L[** *path* **] [-X]** | **-t** *data-file* |

**--simulate** *spec* }

Algorithm options:

**[ --max-cpu *cpu-ratio* ]**

**[ --min-disk *disk-ratio* ]**

**[ -O *name...* ]**

Request options:

**[--disk-template** *template* **]**

**[--standard-alloc** *disk,ram,cpu*  **]**

**[--tiered-alloc** *disk,ram,cpu* **]**

Output options:

**[--machine-readable**[=*CHOICE*] **]**

**[-p**[*fields*]**]**

DESCRIPTION

-----------

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

iallocator plugin in *allocate* mode.

The output of the program is designed either for human consumption (the

default) or, when enabled with the ``--machine-readable`` option

(described further below), for machine consumption. In the latter case,

it is intended 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 machine-readable output of the

script (all prefixed with *HTS_*):

SPEC_MEM, SPEC_DSK, SPEC_CPU, SPEC_RQN, SPEC_DISK_TEMPLATE

  These represent the specifications of the instance model used for

  allocation (the memory, disk, cpu, requested nodes, disk template).

TSPEC_INI_MEM, TSPEC_INI_DSK, TSPEC_INI_CPU, ...

  Only defined when the tiered mode allocation is enabled, these are

  similar to the above specifications but show the initial starting spec

  for tiered allocation.

CLUSTER_MEM, CLUSTER_DSK, CLUSTER_CPU, CLUSTER_NODES

  These represent the total memory, disk, CPU count and total nodes in

  the cluster.

INI_SCORE, FIN_SCORE

  These are the initial (current) and final cluster score (see the hbal

  man page for details about the scoring algorithm).

INI_INST_CNT, FIN_INST_CNT

  The initial and final instance count.

INI_MEM_FREE, FIN_MEM_FREE

  The initial and final total free memory in the cluster (but this

  doesn't necessarily mean available for use).

INI_MEM_AVAIL, FIN_MEM_AVAIL

  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.

INI_MEM_RESVD, FIN_MEM_RESVD

  The initial and final reserved memory (for redundancy/N+1 purposes).

INI_MEM_INST, FIN_MEM_INST

  The initial and final memory used for instances (actual runtime used

  RAM).

INI_MEM_OVERHEAD, FIN_MEM_OVERHEAD

  The initial and final memory overhead--memory used for the node

  itself and unacounted memory (e.g. due to hypervisor overhead).

INI_MEM_EFF, HTS_INI_MEM_EFF

  The initial and final memory efficiency, represented as instance

  memory divided by total memory.

INI_DSK_FREE, INI_DSK_AVAIL, INI_DSK_RESVD, INI_DSK_INST, INI_DSK_EFF

  Initial disk stats, similar to the memory ones.

FIN_DSK_FREE, FIN_DSK_AVAIL, FIN_DSK_RESVD, FIN_DSK_INST, FIN_DSK_EFF

  Final disk stats, similar to the memory ones.

INI_CPU_INST, FIN_CPU_INST

  Initial and final number of virtual CPUs used by instances.

INI_CPU_EFF, FIN_CPU_EFF

  The initial and final CPU efficiency, represented as the count of

  virtual instance CPUs divided by the total physical CPU count.

INI_MNODE_MEM_AVAIL, FIN_MNODE_MEM_AVAIL

  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.

INI_MNODE_DSK_AVAIL, FIN_MNODE_DSK_AVAIL

  Like the above but for disk.

TSPEC

  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

  2560,102400,2=20 512,102400,2=21**.

KM_USED_CPU, KM_USED_NPU, KM_USED_MEM, KM_USED_DSK

  These represents the metrics of used resources at the start of the

  computation (only for tiered allocation mode). The NPU value is

  "normalized" CPU count, i.e. the number of virtual CPUs divided by

  the maximum ratio of the virtual to physical CPUs.

KM_POOL_CPU, KM_POOL_NPU, 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_POOL_NPU, 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.

ALLOC_USAGE

  The current usage represented as initial number of instances divided

  per final number of instances.

ALLOC_COUNT

  The number of instances allocated (delta between FIN_INST_CNT and

  INI_INST_CNT).

ALLOC_FAIL*_CNT

  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.

ALLOC_FAIL_REASON

  The reason for most of the failures, being one of the above FAIL*

  strings.

OK

  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

  relied upon.

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 human output format should be self-explanatory, so it is not

described further.

OPTIONS

-------

The options that can be passed to the program are as follows:

--disk-template *template*

  The disk template for the instance; one of the Ganeti disk templates

  (e.g. plain, drbd, so on) should be passed in.

--max-cpu=*cpu-ratio*

  The maximum virtual to physical cpu ratio, as a floating point number

  greater than or equal to 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

  exactly one means there will be no over-subscription of CPU (except

  for the CPU time used by the node itself), and values below one do not

  make sense, as that means other resources (e.g. disk) won't be fully

  utilised due to CPU restrictions.

--min-disk=*disk-ratio*

  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.

-l *rounds*, --max-length=*rounds*

  Restrict the number of instance allocations to this length. This is

  not very useful in practice, but can be used for testing hspace

  itself, or to limit the runtime for very big clusters.

-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.

-O *name*

  This option (which can be given multiple times) will mark nodes as

  being *offline*. This means a couple of things:

  - instances won't be placed on these nodes, not even temporarily;

    e.g. the *replace primary* move is not available if the secondary

    node is offline, since this move requires a failover.

  - these nodes will not be included in the score calculation (except

    for the percentage of instances on offline nodes)

  Note that the algorithm will also mark as offline any nodes which

  are reported by RAPI as such, or that have "?" in file-based input

  in any numeric fields.

-S *filename*, --save-cluster=*filename*

  If given, the state of the cluster at the end of the allocation is

  saved to a file named *filename.alloc*, and if tiered allocation is

  enabled, the state after tiered allocation will be saved to

  *filename.tiered*. This allows re-feeding the cluster state to

  either hspace itself (with different parameters) or for example

  hbal, via the ``-t`` option.

-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).

-m *cluster*

  Backend specification: collect data directly from the *cluster* given

  as an argument via RAPI. The option is described in the man page

  **htools**(1).

-L [*path*]

  Backend specification: collect data directly from the master daemon,

  which is to be contacted via LUXI (an internal Ganeti protocol). The

  option is described in the man page **htools**(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).

--standard-alloc *disk,ram,cpu*

  This option specifies the instance size for the *standard* allocation

  mode, where we simply allocate instances of the same, fixed size until

  the cluster runs out of space.

  The specification given is similar to the *--simulate* option and it

  holds:

  - the disk size of the instance (units can be used)

  - the memory size of the instance (units can be used)

  - the vcpu count for the insance

  An example description would be *100G,4g,2* describing an instance

  specification of 100GB of disk space, 4GiB of memory and 2 VCPUs.

--tiered-alloc *disk,ram,cpu*

  Besides 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 metric that last failed during allocation. The

  argument should have the same format as for ``-standard-alloc``.

  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.

--machines-readable[=*choice*]

  By default, the output of the program is in "human-readable" format,

  i.e. text descriptions. By passing this flag you can either enable

  (``--machine-readable`` or ``--machine-readable=yes``) or explicitly

  disable (``--machine-readable=no``) the machine readable format

  described above.

-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.

UNITS

~~~~~

By default, all 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.

EXIT STATUS

-----------

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

----

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.

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