Add computation of the failure reason in hspace

[ganeti-local] / hspace.1

.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.

With default options, the output of the program is designed to be
parseable; when the -p option is passed, this is no longer true.

.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 program output.

.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 EXAMPLE

.SS Default output

.in +4n
.nf
.RB "$" " hspace --mem 16 --disk 16 --req-nodes 2"
Initial score: 0.38988095
Initial instances: 3
Initial free RAM: 546
Initial free disk: 260600
Final score: 0.32638889
Final instances: 7
Final free RAM: 482
Final free disk: 260472
Usage: 0.43
Allocations: 4
.fi
.in

This shows that (on this fake cluster), starting from 3 initial
instances, using the hail iallocator plugin, it would be possible to
add four (Allocations: 4) new instances to the cluster.

.SS Verbose output

For the same cluster as above:
.in +4n
.nf
.RB "$" " hspace --mem 16 --disk 16 --req-nodes 2 -v"
Initial score: 0.38988095
Initial instances: 3
Initial free RAM: 546
Initial free disk: 260600
Final score: 0.32638889
Final instances: 7
Final free RAM: 482
Final free disk: 260472
Usage: 0.43
Allocations: 4
Inst: new-0 node2 node1
Inst: new-1 node2 node1
Inst: new-2 node2 node1
Inst: new-3 node2 node1
.fi
.in

The output now includes the placement for the new instances (named
\fBnew-\fInumber\fR).

.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.