Synnefo » snf-ganeti

.TH HSPACE 1 2009-06-01 htools "Ganeti H-tools"

.SH NAME

hspace \- Cluster space analyzer for Ganeti

.SH SYNOPSIS

.B hspace

.B "[backend options...]"

.B "[algorithm options...]"

.B "[request options..."]

.BI "[ -p[" fields "] ]"

.B "[-v... | -q]"

.B hspace

.B --version

.TP

Backend options:

.BI " -m " cluster

|

.BI " -L[" path "]"

|

.BI " -t " data-file

|

.BI " --simulate " spec

.TP

Algorithm options:

.BI "[ --max-cpu " cpu-ratio " ]"

.BI "[ --min-disk " disk-ratio " ]"

.BI "[ -O " name... " ]"

.TP

Request options:

.BI "[--memory " mem "]"

.BI "[--disk " disk "]"

.BI "[--req-nodes " req-nodes "]"

.BI "[--vcpus " vcpus "]"

.BI "[--tiered-alloc " spec "]"

.SH 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.

The output of the program is designed to interpreted as a shell

fragment (or parsed as a \fIkey=value\fR 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 \fIHTS_\fR):

.TP

.I 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).

.TP

.I CLUSTER_MEM, CLUSTER_DSK, CLUSTER_CPU, CLUSTER_NODES

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

the cluster.

.TP

.I INI_SCORE, FIN_SCORE

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

man page for details about the scoring algorithm).

.TP

.I INI_INST_CNT, FIN_INST_CNT

The initial and final instance count.

.TP

.I 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).

.TP

.I 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.

.TP

.I INI_MEM_RESVD, FIN_MEM_RESVD

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

.TP

.I INI_MEM_INST, FIN_MEM_INST

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

RAM).

.TP

.I INI_MEM_OVERHEAD, FIN_MEM_OVERHEAD

The initial and final memory overhead \(em memory used for the node

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

.TP

.I INI_MEM_EFF, HTS_INI_MEM_EFF

The initial and final memory efficiency, represented as instance

memory divided by total memory.

.TP

.I INI_DSK_FREE, INI_DSK_AVAIL, INI_DSK_RESVD, INI_DSK_INST, INI_DSK_EFF

Initial disk stats, similar to the memory ones.

.TP

.I FIN_DSK_FREE, FIN_DSK_AVAIL, FIN_DSK_RESVD, FIN_DSK_INST, FIN_DSK_EFF

Final disk stats, similar to the memory ones.

.TP

.I INI_CPU_INST, FIN_CPU_INST

Initial and final number of virtual CPUs used by instances.

.TP

.I 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.

.TP

.I INI_MNODE_MEM_AVAIL, FIN_MNODE_MEM_AVAIL

The initial and final maximum per\(hynode 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.

.TP

.I INI_MNODE_DSK_AVAIL, FIN_MNODE_DSK_AVAIL

Like the above but for disk.

.TP

.I 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\(hyseparated list

of values; each value is of the form \fImemory,disk,vcpu=count\fR

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: \fB4096,102400,2=225

2560,102400,2=20 512,102400,2=21\fR.

.TP

.I 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.

.TP

.I 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.

.TP

.I 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 \fI--max-cpu\fR

option hasn't been specified this will be \-1.

.TP

.I ALLOC_USAGE

The current usage represented as initial number of instances divided

per final number of instances.

.TP

.I ALLOC_COUNT

The number of instances allocated (delta between FIN_INST_CNT and

INI_INST_CNT).

.TP

.I 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.

.TP

.I ALLOC_FAIL_REASON

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

strings.

.TP

.I 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.

.PP

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.

.SH OPTIONS

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

.TP

.BI "--memory " mem

The memory size of the instances to be placed (defaults to 4GiB).

.TP

.BI "--disk " disk

The disk size of the instances to be placed (defaults to 100GiB).

.TP

.BI "--req-nodes " num-nodes

The number of nodes for the instances; the default of two means

mirrored instances, while passing one means plain type instances.

.TP

.BI "--vcpus " vcpus

The number of VCPUs of the instances to be placed (defaults to 1).

.TP

.BI "--max-cpu " cpu-ratio

The maximum virtual\(hyto\(hyphysical cpu ratio, as a floating point

number between zero and one. For example, specifying \fIcpu-ratio\fR

as \fB2.5\fR means that, for a 4\(hycpu 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.

.TP

.BI "--min-disk " disk-ratio

The minimum amount of free disk space remaining, as a floating point

number. For example, specifying \fIdisk-ratio\fR as \fB0.25\fR means

that at least one quarter of disk space should be left free on nodes.

.TP

.B -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.

It is possible to customise the listed information by passing a

comma\(hyseparated 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:

.RS

.TP

.B F

a character denoting the status of the node, with '\-' meaning an

offline node, '*' meaning N+1 failure and blank meaning a good node

.TP

.B Name

the node name

.TP

.B t_mem

the total node memory

.TP

.B n_mem

the memory used by the node itself

.TP

.B i_mem

the memory used by instances

.TP

.B x_mem

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

.TP

.B f_mem

the free node memory

.TP

.B r_mem

the reserved node memory, which is the amount of free memory needed

for N+1 compliance

.TP

.B t_dsk

total disk

.TP

.B f_dsk

free disk

.TP

.B pcpu

the number of physical cpus on the node

.TP

.B vcpu

the number of virtual cpus allocated to primary instances

.TP

.B pcnt

number of primary instances

.TP

.B pcnt

number of secondary instances

.TP

.B p_fmem

percent of free memory

.TP

.B p_fdsk

percent of free disk

.TP

.B r_cpu

ratio of virtual to physical cpus

.TP

.B lCpu

the dynamic CPU load (if the information is available)

.TP

.B lMem

the dynamic memory load (if the information is available)

.TP

.B lDsk

the dynamic disk load (if the information is available)

.TP

.B lNet

the dynamic net load (if the information is available)

.RE

.TP

.BI "-O " name

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

being \fIoffline\fR, 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\(hybased input in any

numeric fields.

.RE

.TP

.BI "-t" datafile ", --text-data=" datafile

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.

.TP

.BI "-S" filename ", --save-cluster=" filename

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

saved to a file named \fIfilename.alloc\fR, and if tiered allocation

is enabled, the state after tiered allocation will be saved to

\fIfilename.tiered\fR. This allows re-feeding the cluster state to

either hspace itself (with different parameters) or for example hbal.

.TP

.BI "-m" cluster

Collect data directly from the

.I cluster

given as an argument via RAPI. If the argument doesn't contain a colon

(:), then it is converted into a fully\(hybuilt URL via prepending

https:// and appending the default RAPI port, otherwise it's

considered a fully\(hyspecified URL and is used as\(hyis.

.TP

.BI "-L[" path "]"

Collect data directly from the master daemon, which is to be contacted

via the luxi (an internal Ganeti protocol). An optional \fIpath\fR

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 \fI--localstatedir=/var\fR is used.

.TP

.BI "--simulate " description

Instead of using actual data, build an empty cluster given a node

description. The \fIdescription\fR parameter must be a

comma\(hyseparated list of four elements, describing in order:

.RS

.RS

.TP

the number of nodes in the cluster

.TP

the disk size of the nodes, in mebibytes

.TP

the memory size of the nodes, in mebibytes

.TP

the cpu core count for the nodes

.RE

An example description would be \fB20,102400,16384,4\fR describing a

20\(hynode 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

currently.

.RE

.TP

.BI "--tiered-alloc " spec

Beside the standard, fixed\(hysize 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 \fI--simulate\fR option and it

holds:

.RS

.RS

.TP

the disk size of the instance

.TP

the memory size of the instance

.TP

the vcpu count for the insance

.RE

An example description would be \fB10240,8192,2\fR 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.

.RE

.TP

.B -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. At verbosity 2 the location of the new instances is

shown in the standard error.

.TP

.B -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.

.TP

.B -V, --version

Just show the program version and exit.

.SH 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).

.SH 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.

.SH ENVIRONMENT

If the variables \fBHTOOLS_NODES\fR and \fBHTOOLS_INSTANCES\fR 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.

.SH SEE ALSO

.BR hbal "(1), " hscan "(1), " ganeti "(7), " gnt-instance "(8), "

.BR gnt-node "(8)"

.SH "COPYRIGHT"

.PP

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.

.PP

On Debian systems, the complete text of the GNU General Public License

can be found in /usr/share/common-licenses/GPL.