Provided by: ganeti-htools_2.9.3-1_amd64 bug

NAME

       hbal - Cluster balancer for Ganeti

SYNOPSIS

       hbal {backend options...} [algorithm options...] [reporting options...]

       hbal --version

       Backend options:

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

       Algorithm options:

       [ --max-cpu cpu-ratio ] [ --min-disk disk-ratio ] [ -l limit ] [ -e score ] [ -g delta ] [
       --min-gain-limit threshold ] [ -O name...  ] [ --no-disk-moves ] [ --no-instance-moves ] [
       -U  util-file  ]  [  --evac-mode  ]  [  --select-instances inst... ] [ --exclude-instances
       inst... ]

       Reporting options:

       [ -C[ file ] ] [ -p[ fields ] ] [ --print-instances ] [ -S file ] [ -v... | -q ]

DESCRIPTION

       hbal is a cluster balancer that looks at the current state  of  the  cluster  (nodes  with
       their total and free disk, memory, etc.)
        and  instance placement and computes a series of steps designed to bring the cluster into
       a better state.

       The algorithm used is designed to be stable (i.e.  it will give you the same results  when
       restarting  it  from the middle of the solution) and reasonably fast.  It is not, however,
       designed to be a perfect algorithm: it is possible to make it go into a corner from  which
       it can find no improvement, because it looks only one "step" ahead.

       By  default,  the  program  will  show  the solution incrementally as it is computed, in a
       somewhat cryptic format; for getting the actual Ganeti command list, use the -C option.

   ALGORITHM
       The program works in independent steps; at each step, we compute the  best  instance  move
       that lowers the cluster score.

       The  possible  move type for an instance are combinations of failover/migrate and replace-
       disks such that we change one of the instance  nodes,  and  the  other  one  remains  (but
       possibly with changed role, e.g.  from primary it becomes secondary).  The list is:

       · failover (f)

       · replace secondary (r)

       · replace primary, a composite move (f, r, f)

       · failover and replace secondary, also composite (f, r)

       · replace secondary and failover, also composite (r, f)

       We  don't  do  the  only  remaining  possibility  of  replacing both nodes (r,f,r,f or the
       equivalent f,r,f,r) since these move  needs  an  exhaustive  search  over  both  candidate
       primary  and  secondary  nodes,  and  is  O(n*n)  in the number of nodes.  Furthermore, it
       doesn't seems to give better scores but will result in more disk replacements.

   PLACEMENT RESTRICTIONS
       At each step, we prevent an instance move if it would cause:

       · a node to go into N+1 failure state

       · an instance to move onto an offline node (offline nodes are either read from the cluster
         or declared with -O; drained nodes are considered offline)

       · an exclusion-tag based conflict (exclusion tags are read from the cluster and/or defined
         via the --exclusion-tags option)

       · a max vcpu/pcpu ratio to be exceeded (configured via --max-cpu)

       · min disk free percentage to go below the configured limit (configured via --min-disk)

   CLUSTER SCORING
       As said before, the algorithm tries to minimise the cluster score at each step.  Currently
       this score is computed as a weighted sum of the following components:

       · standard deviation of the percent of free memory

       · standard deviation of the percent of reserved memory

       · standard deviation of the percent of free disk

       · count of nodes failing N+1 check

       · count  of  instances  living  (either  as primary or secondary) on offline nodes; in the
         sense of hbal (and the other htools) drained nodes are considered offline

       · count of instances living (as primary) on offline nodes; this  differs  from  the  above
         metric by helping failover of such instances in 2-node clusters

       · standard  deviation  of  the ratio of virtual-to-physical cpus (for primary instances of
         the node)

       · standard deviation of the dynamic load on the nodes, for cpus, memory, disk and network

       The free memory and free disk values help ensure that all nodes are somewhat  balanced  in
       their  resource  usage.   The  reserved  memory  helps  to  ensure that nodes are somewhat
       balanced in holding secondary instances, and that no node keeps too much  memory  reserved
       for  N+1.   And  finally, the N+1 percentage helps guide the algorithm towards eliminating
       N+1 failures, if possible.

       Except for the N+1 failures and offline instances counts, we use  the  standard  deviation
       since  when  used  with  values  within a fixed range (we use percents expressed as values
       between zero and one) it gives consistent results across all metrics (there are some small
       issues  related to different means, but it works generally well).  The 'count' type values
       will have higher score and thus will matter more for balancing; thus these are better  for
       hard  constraints  (like  evacuating  nodes  and  fixing  N+1 failures).  For example, the
       offline instances count (i.e.  the number of instances living on offline nodes) will cause
       the  algorithm to actively move instances away from offline nodes.  This, coupled with the
       restriction on placement given by offline nodes, will cause evacuation of such nodes.

       The dynamic load values need to be read from  an  external  file  (Ganeti  doesn't  supply
       them), and are computed for each node as: sum of primary instance cpu load, sum of primary
       instance memory load, sum of primary and secondary instance disk load (as  DRBD  generates
       write  load  on  secondary  nodes  too  in normal case and in degraded scenarios also read
       load), and sum of primary instance network load.  An example  of  how  to  generate  these
       values  for  input  to  hbal  would  be  to  track xm list for instances over a day and by
       computing the delta of the cpu values, and feed that via the -U option for  all  instances
       (and  keep  the  other  metrics as one).  For the algorithm to work, all that is needed is
       that the values are consistent for a metric across all instances (e.g.  all instances  use
       cpu%  to  report cpu usage, and not something related to number of CPU seconds used if the
       CPUs are different), and that they are normalised to between zero and one.  Note that it's
       recommended  to  not  have  zero  as  the  load  value  for any instance metric since then
       secondary instances are not well balanced.

       On a perfectly balanced cluster (all nodes the same size, all instances the same size  and
       spread  across the nodes equally), the values for all metrics would be zero.  This doesn't
       happen too often in practice :)

   OFFLINE INSTANCES
       Since current Ganeti versions do not report the memory used by offline  (down)  instances,
       ignoring  the run status of instances will cause wrong calculations.  For this reason, the
       algorithm subtracts the memory size of down instances from the free node memory  of  their
       primary node, in effect simulating the startup of such instances.

   EXCLUSION TAGS
       The  exclusion tags mechanism is designed to prevent instances which run the same workload
       (e.g.  two DNS servers) to land on the same node, which would make the respective  node  a
       SPOF for the given service.

       It  works by tagging instances with certain tags and then building exclusion maps based on
       these.  Which tags are actually used is configured either via  the  command  line  (option
       --exclusion-tags) or via adding them to the cluster tags:

       --exclusion-tags=a,b
              This  will  make  all  instance  tags  of  the  form a:*, b:* be considered for the
              exclusion map

       cluster tags htools:iextags:a, htools:iextags:b
              This will make instance tags a:*, b:* be considered for the  exclusion  map.   More
              precisely, the suffix of cluster tags starting with htools:iextags: will become the
              prefix of the exclusion tags.

       Both the above forms mean that two instances both having (e.g.)
        the tag a:foo or b:bar won't end on the same node.

OPTIONS

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

       -C, --print-commands
              Print the command list at the end of the run.  Without this, the program will  only
              show a shorter, but cryptic output.

              Note  that  the  moves list will be split into independent steps, called "jobsets",
              but only for visual inspection,  not  for  actually  parallelisation.   It  is  not
              possible  to  parallelise these directly when executed via "gnt-instance" commands,
              since a compound command  (e.g.   failover  and  replace-disks)  must  be  executed
              serially.   Parallel execution is only possible when using the Luxi backend and the
              -L option.

              The algorithm for splitting the moves into jobsets is by accumulating  moves  until
              the next move is touching nodes already touched by the current moves; this means we
              can't execute in parallel (due to resource allocation in Ganeti) and thus we  start
              a new jobset.

       -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.

       --print-instances
              Prints  the before and after instance map.  This is less useful as the node status,
              but it can help in understanding instance moves.

       -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 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.

       -e score, --min-score=score
              This  parameter  denotes  the  minimum  score  we  are  happy  with  and alters the
              computation in two ways:

              · if the cluster has the initial score lower than this value, then we  don't  enter
                the algorithm at all, and exit with success

              · during  the iterative process, if we reach a score lower than this value, we exit
                the algorithm

              The default value of the parameter is currently 1e-9 (chosen empirically).

       -g delta, --min-gain=delta
              Since the balancing algorithm can sometimes result in just very tiny  improvements,
              that  bring less gain that they cost in relocation time, this parameter (defaulting
              to 0.01) represents the  minimum  gain  we  require  during  a  step,  to  continue
              balancing.

       --min-gain-limit=threshold
              The  above  min-gain  option  will only take effect if the cluster score is already
              below threshold (defaults to 0.1).  The rationale behind this setting  is  that  at
              high cluster scores (badly balanced clusters), we don't want to abort the rebalance
              too quickly, as later  gains  might  still  be  significant.   However,  under  the
              threshold, the total gain is only the threshold value, so we can exit early.

       --no-disk-moves
              This  parameter  prevents  hbal  from using disk move (i.e.  "gnt-instance replace-
              disks") operations.  This will result in a much quicker balancing,  but  of  course
              the  improvements  are  limited.  It is up to the user to decide when to use one or
              another.

       --no-instance-moves
              This parameter  prevents  hbal  from  using  instance  moves  (i.e.   "gnt-instance
              migrate/failover")  operations.   This  will  only  use  the  slow disk-replacement
              operations, and will also provide a worse balance, but  can  be  useful  if  moving
              instances around is deemed unsafe or not preferred.

       --evac-mode
              This  parameter  restricts  the list of instances considered for moving to the ones
              living on offline/drained nodes.  It can  be  used  as  a  (bulk)  replacement  for
              Ganeti's  own  gnt-node  evacuate,  with  the  note  that it doesn't guarantee full
              evacuation.

       --select-instances=instances
              This parameter marks the given instances (as a comma-separated list)  as  the  only
              ones being moved during the rebalance.

       --exclude-instances=instances
              This  parameter  marks  the  given instances (as a comma-separated list) from being
              moved during the rebalance.

       -U util-file
              This parameter specifies a file holding instance  dynamic  utilisation  information
              that  will  be  used to tweak the balancing algorithm to equalise load on the nodes
              (as opposed to static resource usage).  The file is in  the  format  "instance_name
              cpu_util  mem_util disk_util net_util" where the "_util" parameters are interpreted
              as numbers and the instance name must match  exactly  the  instance  as  read  from
              Ganeti.  In case of unknown instance names, the program will abort.

              If  not  given,  the  default  values  are  one  for  all  metrics and thus dynamic
              utilisation has only one effect on the algorithm: the equalisation of the secondary
              instances  across  nodes  (this  is the only metric that is not tracked by another,
              dedicated value, and thus the disk load of instances will cause secondary  instance
              equalisation).   Note  that  value  of one will also influence slightly the primary
              instance count, but that  is  already  tracked  via  other  metrics  and  thus  the
              influence of the dynamic utilisation will be practically insignificant.

       -S filename, --save-cluster=filename
              If  given, the state of the cluster before the balancing is saved to the given file
              plus the extension "original" (i.e.  filename.original), and the state at  the  end
              of  the  balancing  is  saved to the given file plus the extension "balanced" (i.e.
              filename.balanced).  This allows re-feeding the cluster state to either hbal itself
              or for example hspace 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).

       -X     When using the Luxi backend,  hbal  can  also  execute  the  given  commands.   The
              execution  method  is  to  execute  the  individual  jobsets (see the -C option for
              details) in separate stages, aborting if at any time a jobset doesn't have all jobs
              successful.   Each  step  in the balancing solution will be translated into exactly
              one Ganeti job (having between one and three OpCodes),  and  all  the  steps  in  a
              jobset will be executed in parallel.  The jobsets themselves are executed serially.

              The execution of the job series can be interrupted, see below for signal handling.

       -l N, --max-length=N
              Restrict the solution to this length.  This can be used for example to automate the
              execution of the balancing.

       --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.

       -G uuid, --group=uuid
              On an multi-group cluster, select this group for processing.  Otherwise  hbal  will
              abort, since it cannot balance multiple groups at the same time.

       -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.

SIGNAL HANDLING

       When  executing  jobs  via LUXI (using the -X option), normally hbal will execute all jobs
       until either one errors out or all the jobs finish successfully.

       Since balancing can take a long time, it is possible to stop hbal early in two ways:

       · by sending a SIGINT (^C), hbal will register the  termination  request,  and  will  wait
         until the currently submitted jobs finish, at which point it will exit (with exit code 0
         if all jobs finished correctly, otherwise with exit code 1 as usual)

       · by sending a SIGTERM, hbal  will  immediately  exit  (with  exit  code  2);  it  is  the
         responsibility  of  the  user  to  follow  up  with  Ganeti  and check the result of the
         currently-executing jobs

       Note that in any situation, it's perfectly safe to kill hbal, either via the above signals
       or  via any other signal (e.g.  SIGQUIT, SIGKILL), since the jobs themselves are processed
       by Ganeti whereas hbal (after submission) only watches their progression.  In  this  case,
       the user will have to query Ganeti for job results.

EXIT STATUS

       The  exit  status of the command will be zero, unless for some reason the algorithm failed
       (e.g.  wrong node or instance data), invalid command line options,  or  (in  case  of  job
       execution) one of the jobs has failed.

       Once  job execution via Luxi has started (-X), if the balancing was interrupted early (via
       SIGINT, or via --max-length) but all jobs executed successfully, then the exit  status  is
       zero;  a  non-zero  exit code means that the cluster state should be investigated, since a
       job failed or we couldn't compute its status and this can also point to a problem  on  the
       Ganeti side.

BUGS

       The  program  does  not check all its input data for consistency, and sometime aborts with
       cryptic errors messages with invalid data.

       The algorithm is not perfect.

EXAMPLE

       Note that these examples are not for the latest version (they don't have full node data).

   Default output
       With the default options, the program shows each individual step and the  improvements  it
       brings in cluster score:

              $ hbal
              Loaded 20 nodes, 80 instances
              Cluster is not N+1 happy, continuing but no guarantee that the cluster will end N+1 happy.
              Initial score: 0.52329131
              Trying to minimize the CV...
                  1. instance14  node1:node10  => node16:node10 0.42109120 a=f r:node16 f
                  2. instance54  node4:node15  => node16:node15 0.31904594 a=f r:node16 f
                  3. instance4   node5:node2   => node2:node16  0.26611015 a=f r:node16
                  4. instance48  node18:node20 => node2:node18  0.21361717 a=r:node2 f
                  5. instance93  node19:node18 => node16:node19 0.16166425 a=r:node16 f
                  6. instance89  node3:node20  => node2:node3   0.11005629 a=r:node2 f
                  7. instance5   node6:node2   => node16:node6  0.05841589 a=r:node16 f
                  8. instance94  node7:node20  => node20:node16 0.00658759 a=f r:node16
                  9. instance44  node20:node2  => node2:node15  0.00438740 a=f r:node15
                 10. instance62  node14:node18 => node14:node16 0.00390087 a=r:node16
                 11. instance13  node11:node14 => node11:node16 0.00361787 a=r:node16
                 12. instance19  node10:node11 => node10:node7  0.00336636 a=r:node7
                 13. instance43  node12:node13 => node12:node1  0.00305681 a=r:node1
                 14. instance1   node1:node2   => node1:node4   0.00263124 a=r:node4
                 15. instance58  node19:node20 => node19:node17 0.00252594 a=r:node17
              Cluster score improved from 0.52329131 to 0.00252594

       In the above output, we can see:

       · the input data (here from files) shows a cluster with 20 nodes and 80 instances

       · the cluster is not initially N+1 compliant

       · the initial score is 0.52329131

       The  step list follows, showing the instance, its initial primary/secondary nodes, the new
       primary secondary, the cluster list, and the actions taken in this step (with 'f' denoting
       failover/migrate and 'r' denoting replace secondary).

       Finally, the program shows the improvement in cluster score.

       A more detailed output is obtained via the -C and -p options:

              $ hbal
              Loaded 20 nodes, 80 instances
              Cluster is not N+1 happy, continuing but no guarantee that the cluster will end N+1 happy.
              Initial cluster status:
              N1 Name   t_mem f_mem r_mem t_dsk f_dsk pri sec  p_fmem  p_fdsk
               * node1  32762  1280  6000  1861  1026   5   3 0.03907 0.55179
                 node2  32762 31280 12000  1861  1026   0   8 0.95476 0.55179
               * node3  32762  1280  6000  1861  1026   5   3 0.03907 0.55179
               * node4  32762  1280  6000  1861  1026   5   3 0.03907 0.55179
               * node5  32762  1280  6000  1861   978   5   5 0.03907 0.52573
               * node6  32762  1280  6000  1861  1026   5   3 0.03907 0.55179
               * node7  32762  1280  6000  1861  1026   5   3 0.03907 0.55179
                 node8  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node9  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
               * node10 32762  7280 12000  1861  1026   4   4 0.22221 0.55179
                 node11 32762  7280  6000  1861   922   4   5 0.22221 0.49577
                 node12 32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node13 32762  7280  6000  1861   922   4   5 0.22221 0.49577
                 node14 32762  7280  6000  1861   922   4   5 0.22221 0.49577
               * node15 32762  7280 12000  1861  1131   4   3 0.22221 0.60782
                 node16 32762 31280     0  1861  1860   0   0 0.95476 1.00000
                 node17 32762  7280  6000  1861  1106   5   3 0.22221 0.59479
               * node18 32762  1280  6000  1396   561   5   3 0.03907 0.40239
               * node19 32762  1280  6000  1861  1026   5   3 0.03907 0.55179
                 node20 32762 13280 12000  1861   689   3   9 0.40535 0.37068

              Initial score: 0.52329131
              Trying to minimize the CV...
                  1. instance14  node1:node10  => node16:node10 0.42109120 a=f r:node16 f
                  2. instance54  node4:node15  => node16:node15 0.31904594 a=f r:node16 f
                  3. instance4   node5:node2   => node2:node16  0.26611015 a=f r:node16
                  4. instance48  node18:node20 => node2:node18  0.21361717 a=r:node2 f
                  5. instance93  node19:node18 => node16:node19 0.16166425 a=r:node16 f
                  6. instance89  node3:node20  => node2:node3   0.11005629 a=r:node2 f
                  7. instance5   node6:node2   => node16:node6  0.05841589 a=r:node16 f
                  8. instance94  node7:node20  => node20:node16 0.00658759 a=f r:node16
                  9. instance44  node20:node2  => node2:node15  0.00438740 a=f r:node15
                 10. instance62  node14:node18 => node14:node16 0.00390087 a=r:node16
                 11. instance13  node11:node14 => node11:node16 0.00361787 a=r:node16
                 12. instance19  node10:node11 => node10:node7  0.00336636 a=r:node7
                 13. instance43  node12:node13 => node12:node1  0.00305681 a=r:node1
                 14. instance1   node1:node2   => node1:node4   0.00263124 a=r:node4
                 15. instance58  node19:node20 => node19:node17 0.00252594 a=r:node17
              Cluster score improved from 0.52329131 to 0.00252594

              Commands to run to reach the above solution:
                echo step 1
                echo gnt-instance migrate instance14
                echo gnt-instance replace-disks -n node16 instance14
                echo gnt-instance migrate instance14
                echo step 2
                echo gnt-instance migrate instance54
                echo gnt-instance replace-disks -n node16 instance54
                echo gnt-instance migrate instance54
                echo step 3
                echo gnt-instance migrate instance4
                echo gnt-instance replace-disks -n node16 instance4
                echo step 4
                echo gnt-instance replace-disks -n node2 instance48
                echo gnt-instance migrate instance48
                echo step 5
                echo gnt-instance replace-disks -n node16 instance93
                echo gnt-instance migrate instance93
                echo step 6
                echo gnt-instance replace-disks -n node2 instance89
                echo gnt-instance migrate instance89
                echo step 7
                echo gnt-instance replace-disks -n node16 instance5
                echo gnt-instance migrate instance5
                echo step 8
                echo gnt-instance migrate instance94
                echo gnt-instance replace-disks -n node16 instance94
                echo step 9
                echo gnt-instance migrate instance44
                echo gnt-instance replace-disks -n node15 instance44
                echo step 10
                echo gnt-instance replace-disks -n node16 instance62
                echo step 11
                echo gnt-instance replace-disks -n node16 instance13
                echo step 12
                echo gnt-instance replace-disks -n node7 instance19
                echo step 13
                echo gnt-instance replace-disks -n node1 instance43
                echo step 14
                echo gnt-instance replace-disks -n node4 instance1
                echo step 15
                echo gnt-instance replace-disks -n node17 instance58

              Final cluster status:
              N1 Name   t_mem f_mem r_mem t_dsk f_dsk pri sec  p_fmem  p_fdsk
                 node1  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node2  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node3  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node4  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node5  32762  7280  6000  1861  1078   4   5 0.22221 0.57947
                 node6  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node7  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node8  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node9  32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node10 32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node11 32762  7280  6000  1861  1022   4   4 0.22221 0.54951
                 node12 32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node13 32762  7280  6000  1861  1022   4   4 0.22221 0.54951
                 node14 32762  7280  6000  1861  1022   4   4 0.22221 0.54951
                 node15 32762  7280  6000  1861  1031   4   4 0.22221 0.55408
                 node16 32762  7280  6000  1861  1060   4   4 0.22221 0.57007
                 node17 32762  7280  6000  1861  1006   5   4 0.22221 0.54105
                 node18 32762  7280  6000  1396   761   4   2 0.22221 0.54570
                 node19 32762  7280  6000  1861  1026   4   4 0.22221 0.55179
                 node20 32762 13280  6000  1861  1089   3   5 0.40535 0.58565

       Here  we  see,  beside the step list, the initial and final cluster status, with the final
       one showing all nodes being N+1 compliant,  and  the  command  list  to  reach  the  final
       solution.  In the initial listing, we see which nodes are not N+1 compliant.

       The  algorithm  is  stable as long as each step above is fully completed, e.g.  in step 8,
       both the migrate and the replace-disks are done.  Otherwise, if only the migrate is  done,
       the  input data is changed in a way that the program will output a different solution list
       (but hopefully will end in the same state).

REPORTING BUGS

       Report  bugs  to  project  website  (http://code.google.com/p/ganeti/)  or   contact   the
       developers using the Ganeti mailing list (ganeti@googlegroups.com).

SEE ALSO

       Ganeti  overview  and specifications: ganeti(7) (general overview), ganeti-os-interface(7)
       (guest OS definitions), ganeti-extstorage-interface(7) (external storage providers).

       Ganeti  commands:  gnt-cluster(8)   (cluster-wide   commands),   gnt-job(8)   (job-related
       commands),  gnt-node(8) (node-related commands), gnt-instance(8) (instance commands), gnt-
       os(8) (guest OS commands), gnt-storage(8) (storage  commands),  gnt-group(8)  (node  group
       commands), gnt-backup(8) (instance import/export commands), gnt-debug(8) (debug commands).

       Ganeti  daemons:  ganeti-watcher(8) (automatic instance restarter), ganeti-cleaner(8) (job
       queue cleaner), ganeti-noded(8) (node daemon), ganeti-masterd(8) (master daemon),  ganeti-
       rapi(8) (remote API daemon).

       Ganeti htools: htools(1) (generic binary), hbal(1) (cluster balancer), hspace(1) (capacity
       calculation), hail(1) (IAllocator plugin), hscan(1) (data gatherer from remote  clusters),
       hinfo(1) (cluster information printer), mon-collector(7) (data collectors interface).

COPYRIGHT

       Copyright  (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 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.

       On Debian systems, the complete text of the GNU General Public License  can  be  found  in
       /usr/share/common-licenses/GPL.