Synnefo » snf-ganeti » ganeti-local

.TH HAIL 1 2009-03-23 htools "Ganeti H-tools"

.SH NAME

hail \- Ganeti IAllocator plugin

.SH SYNOPSIS

.B hail

.I "input-file"

.B hail

.B --version

.SH DESCRIPTION

hail is a Ganeti IAllocator plugin that allows automatic instance

placement and automatic instance secondary node replacement using the

same algorithm as \fBhbal\fR(1).

The program takes input via a JSON-file containing current cluster

state and the request details, and output (on stdout) a JSON-formatted

response. In case of critical failures, the error message is printed

on stderr and the exit code is changed to show failure.

.SS ALGORITHM

The program uses a simplified version of the hbal algorithm.

For relocations, we try to change the secondary node of the instance

to all the valid other nodes; the node which results in the best

cluster score is chosen.

For single-node allocations (non-mirrored instances), again we select

the node which, when chosen as the primary node, gives the best score.

For dual-node allocations (mirrored instances), we chose the best

pair; this is the only choice where the algoritm is non-trivial

with regard to cluster size.

For all choices, the cluster scoring is identical to the hbal

algorithm.

.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 SEE ALSO

.BR hn1 "(1), " hscan "(1), " ganeti "(7), " gnt-instance "(8), "

.BR gnt-node "(8)"