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 "[-p]"

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

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

.BI "[-m " cluster "]"

.BI "[-n " nodes-file " ]"

.BI "[-i " instances-file "]"

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

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

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

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

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

.B hspace

.B --version

.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 - 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-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.

.TP

.I INI_MNODE_DSK_AVAIL, FIN_MNODE_DSK_AVAIL

Like the above but for disk.

.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.

.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 "--max-cpu " cpu-ratio

The maximum virtual-to-physical 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-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.

.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.

The node list will contain these informations:

.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 pri

number of primary instances

.TP

.B sec

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

.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-based input in any

numeric fields.

.RE

.TP

.BI "-n" nodefile ", --nodes=" nodefile

The name of the file holding node information (if not collecting via

RAPI), instead of the default \fInodes\fR file (but see below how to

customize the default value via the environment).

.TP

.BI "-i" instancefile ", --instances=" instancefile

The name of the file holding instance information (if not collecting

via RAPI), instead of the default \fIinstances\fR file (but see below

how to customize the default value via the environment).

.TP

.BI "-m" cluster

Collect data not from files but 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-built URL via prepending

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

considered a fully-specified URL and is used as-is.

.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 RAPI is 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.