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HSPACE(1) Ganeti | Version @GANETI_VERSION@ |
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=========================================== |
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|
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NAME |
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---- |
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|
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hspace - Cluster space analyzer for Ganeti |
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|
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SYNOPSIS |
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-------- |
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|
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**hspace** {backend options...} [algorithm options...] [request options...] |
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[ -p [*fields*] ] [-v... | -q] |
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|
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**hspace** --version |
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|
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Backend options: |
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|
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{ **-m** *cluster* | **-L[** *path* **] [-X]** | **-t** *data-file* | |
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**--simulate** *spec* } |
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|
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|
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Algorithm options: |
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|
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**[ --max-cpu *cpu-ratio* ]** |
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**[ --min-disk *disk-ratio* ]** |
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**[ -O *name...* ]** |
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|
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|
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Request options: |
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|
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**[--memory** *mem* **]** |
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**[--disk** *disk* **]** |
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**[--disk-template** *template* **]** |
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**[--vcpus** *vcpus* **]** |
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**[--tiered-alloc** *spec* **]** |
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|
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|
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DESCRIPTION |
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----------- |
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|
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|
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hspace computes how many additional instances can be fit on a cluster, |
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while maintaining N+1 status. |
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|
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The program will try to place instances, all of the same size, on the |
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cluster, until the point where we don't have any N+1 possible |
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allocation. It uses the exact same allocation algorithm as the hail |
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iallocator plugin in *allocate* mode. |
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|
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The output of the program is designed to interpreted as a shell |
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fragment (or parsed as a *key=value* file). Options which extend the |
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output (e.g. -p, -v) will output the additional information on stderr |
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(such that the stdout is still parseable). |
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|
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The following keys are available in the output of the script (all |
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prefixed with *HTS_*): |
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|
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SPEC_MEM, SPEC_DSK, SPEC_CPU, SPEC_RQN, SPEC_DISK_TEMPLATE |
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These represent the specifications of the instance model used for |
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allocation (the memory, disk, cpu, requested nodes, disk template). |
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|
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TSPEC_INI_MEM, TSPEC_INI_DSK, TSPEC_INI_CPU |
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Only defined when the tiered mode allocation is enabled, these are |
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similar to the above specifications but show the initial starting spec |
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for tiered allocation. |
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|
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CLUSTER_MEM, CLUSTER_DSK, CLUSTER_CPU, CLUSTER_NODES |
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These represent the total memory, disk, CPU count and total nodes in |
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the cluster. |
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|
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INI_SCORE, FIN_SCORE |
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These are the initial (current) and final cluster score (see the hbal |
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man page for details about the scoring algorithm). |
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|
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INI_INST_CNT, FIN_INST_CNT |
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The initial and final instance count. |
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|
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INI_MEM_FREE, FIN_MEM_FREE |
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The initial and final total free memory in the cluster (but this |
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doesn't necessarily mean available for use). |
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|
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INI_MEM_AVAIL, FIN_MEM_AVAIL |
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The initial and final total available memory for allocation in the |
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cluster. If allocating redundant instances, new instances could |
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increase the reserved memory so it doesn't necessarily mean the |
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entirety of this memory can be used for new instance allocations. |
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|
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INI_MEM_RESVD, FIN_MEM_RESVD |
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The initial and final reserved memory (for redundancy/N+1 purposes). |
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|
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INI_MEM_INST, FIN_MEM_INST |
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The initial and final memory used for instances (actual runtime used |
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RAM). |
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|
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INI_MEM_OVERHEAD, FIN_MEM_OVERHEAD |
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The initial and final memory overhead--memory used for the node |
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itself and unacounted memory (e.g. due to hypervisor overhead). |
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|
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INI_MEM_EFF, HTS_INI_MEM_EFF |
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The initial and final memory efficiency, represented as instance |
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memory divided by total memory. |
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|
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INI_DSK_FREE, INI_DSK_AVAIL, INI_DSK_RESVD, INI_DSK_INST, INI_DSK_EFF |
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Initial disk stats, similar to the memory ones. |
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|
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FIN_DSK_FREE, FIN_DSK_AVAIL, FIN_DSK_RESVD, FIN_DSK_INST, FIN_DSK_EFF |
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Final disk stats, similar to the memory ones. |
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|
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INI_CPU_INST, FIN_CPU_INST |
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Initial and final number of virtual CPUs used by instances. |
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|
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INI_CPU_EFF, FIN_CPU_EFF |
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The initial and final CPU efficiency, represented as the count of |
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virtual instance CPUs divided by the total physical CPU count. |
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|
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INI_MNODE_MEM_AVAIL, FIN_MNODE_MEM_AVAIL |
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The initial and final maximum per-node available memory. This is not |
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very useful as a metric but can give an impression of the status of |
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the nodes; as an example, this value restricts the maximum instance |
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size that can be still created on the cluster. |
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|
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INI_MNODE_DSK_AVAIL, FIN_MNODE_DSK_AVAIL |
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Like the above but for disk. |
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|
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TSPEC |
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If the tiered allocation mode has been enabled, this parameter holds |
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the pairs of specifications and counts of instances that can be |
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created in this mode. The value of the key is a space-separated list |
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of values; each value is of the form *memory,disk,vcpu=count* where |
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the memory, disk and vcpu are the values for the current spec, and |
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count is how many instances of this spec can be created. A complete |
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value for this variable could be: **4096,102400,2=225 |
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2560,102400,2=20 512,102400,2=21**. |
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|
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KM_USED_CPU, KM_USED_NPU, KM_USED_MEM, KM_USED_DSK |
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These represents the metrics of used resources at the start of the |
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computation (only for tiered allocation mode). The NPU value is |
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"normalized" CPU count, i.e. the number of virtual CPUs divided by |
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the maximum ratio of the virtual to physical CPUs. |
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|
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KM_POOL_CPU, KM_POOL_NPU, KM_POOL_MEM, KM_POOL_DSK |
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These represents the total resources allocated during the tiered |
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allocation process. In effect, they represent how much is readily |
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available for allocation. |
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|
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KM_UNAV_CPU, KM_POOL_NPU, KM_UNAV_MEM, KM_UNAV_DSK |
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These represents the resources left over (either free as in |
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unallocable or allocable on their own) after the tiered allocation |
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has been completed. They represent better the actual unallocable |
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resources, because some other resource has been exhausted. For |
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example, the cluster might still have 100GiB disk free, but with no |
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memory left for instances, we cannot allocate another instance, so |
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in effect the disk space is unallocable. Note that the CPUs here |
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represent instance virtual CPUs, and in case the *--max-cpu* option |
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hasn't been specified this will be -1. |
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|
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ALLOC_USAGE |
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The current usage represented as initial number of instances divided |
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per final number of instances. |
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|
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ALLOC_COUNT |
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The number of instances allocated (delta between FIN_INST_CNT and |
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INI_INST_CNT). |
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|
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ALLOC_FAIL*_CNT |
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For the last attemp at allocations (which would have increased |
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FIN_INST_CNT with one, if it had succeeded), this is the count of |
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the failure reasons per failure type; currently defined are FAILMEM, |
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FAILDISK and FAILCPU which represent errors due to not enough |
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memory, disk and CPUs, and FAILN1 which represents a non N+1 |
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compliant cluster on which we can't allocate instances at all. |
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|
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ALLOC_FAIL_REASON |
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The reason for most of the failures, being one of the above FAIL* |
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strings. |
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|
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OK |
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A marker representing the successful end of the computation, and |
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having value "1". If this key is not present in the output it means |
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that the computation failed and any values present should not be |
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relied upon. |
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|
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If the tiered allocation mode is enabled, then many of the INI_/FIN_ |
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metrics will be also displayed with a TRL_ prefix, and denote the |
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cluster status at the end of the tiered allocation run. |
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|
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OPTIONS |
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------- |
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|
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The options that can be passed to the program are as follows: |
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|
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--memory *mem* |
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The memory size of the instances to be placed (defaults to |
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4GiB). Units can be used (see below for more details). |
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|
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--disk *disk* |
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The disk size of the instances to be placed (defaults to |
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100GiB). Units can be used. |
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|
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--disk-template *template* |
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The disk template for the instance; one of the Ganeti disk templates |
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(e.g. plain, drbd, so on) should be passed in. |
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|
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--vcpus *vcpus* |
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The number of VCPUs of the instances to be placed (defaults to 1). |
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|
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--max-cpu=*cpu-ratio* |
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The maximum virtual to physical cpu ratio, as a floating point number |
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greater than or equal to one. For example, specifying *cpu-ratio* as |
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**2.5** means that, for a 4-cpu machine, a maximum of 10 virtual cpus |
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should be allowed to be in use for primary instances. A value of |
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exactly one means there will be no over-subscription of CPU (except |
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for the CPU time used by the node itself), and values below one do not |
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make sense, as that means other resources (e.g. disk) won't be fully |
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utilised due to CPU restrictions. |
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|
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--min-disk=*disk-ratio* |
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The minimum amount of free disk space remaining, as a floating point |
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number. For example, specifying *disk-ratio* as **0.25** means that |
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at least one quarter of disk space should be left free on nodes. |
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|
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-p, --print-nodes |
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Prints the before and after node status, in a format designed to allow |
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the user to understand the node's most important parameters. See the |
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man page **htools**(1) for more details about this option. |
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|
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-O *name* |
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This option (which can be given multiple times) will mark nodes as |
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being *offline*. This means a couple of things: |
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|
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- instances won't be placed on these nodes, not even temporarily; |
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e.g. the *replace primary* move is not available if the secondary |
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node is offline, since this move requires a failover. |
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- these nodes will not be included in the score calculation (except |
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for the percentage of instances on offline nodes) |
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|
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Note that the algorithm will also mark as offline any nodes which |
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are reported by RAPI as such, or that have "?" in file-based input |
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in any numeric fields. |
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|
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-t *datafile*, --text-data=*datafile* |
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The name of the file holding node and instance information (if not |
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collecting via RAPI or LUXI). This or one of the other backends must |
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be selected. |
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|
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-S *filename*, --save-cluster=*filename* |
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If given, the state of the cluster at the end of the allocation is |
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saved to a file named *filename.alloc*, and if tiered allocation is |
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enabled, the state after tiered allocation will be saved to |
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*filename.tiered*. This allows re-feeding the cluster state to |
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either hspace itself (with different parameters) or for example |
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hbal. |
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|
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-m *cluster* |
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Collect data directly from the *cluster* given as an argument via |
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RAPI. If the argument doesn't contain a colon (:), then it is |
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converted into a fully-built URL via prepending ``https://`` and |
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appending the default RAPI port, otherwise it's considered a |
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fully-specified URL and is used as-is. |
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|
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-L [*path*] |
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Collect data directly from the master daemon, which is to be |
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contacted via the luxi (an internal Ganeti protocol). An optional |
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*path* argument is interpreted as the path to the unix socket on |
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which the master daemon listens; otherwise, the default path used by |
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ganeti when installed with *--localstatedir=/var* is used. |
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|
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--simulate *description* |
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Instead of using actual data, build an empty cluster given a node |
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description. The *description* parameter must be a comma-separated |
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list of five elements, describing in order: |
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|
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- the allocation policy for this node group |
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- the number of nodes in the cluster |
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- the disk size of the nodes (default in mebibytes, units can be used) |
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- the memory size of the nodes (default in mebibytes, units can be used) |
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- the cpu core count for the nodes |
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|
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An example description would be **preferred,B20,100G,16g,4** |
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describing a 20-node cluster where each node has 100GB of disk |
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space, 16GiB of memory and 4 CPU cores. Note that all nodes must |
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have the same specs currently. |
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|
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This option can be given multiple times, and each new use defines a |
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new node group. Hence different node groups can have different |
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allocation policies and node count/specifications. |
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|
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--tiered-alloc *spec* |
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Besides the standard, fixed-size allocation, also do a tiered |
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allocation scheme where the algorithm starts from the given |
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specification and allocates until there is no more space; then it |
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decreases the specification and tries the allocation again. The |
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decrease is done on the matric that last failed during |
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allocation. The specification given is similar to the *--simulate* |
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option and it holds: |
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|
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- the disk size of the instance (units can be used) |
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- the memory size of the instance (units can be used) |
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- the vcpu count for the insance |
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|
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An example description would be *100G,4g,2* describing an initial |
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starting specification of 100GB of disk space, 4GiB of memory and 2 |
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VCPUs. |
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|
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Also note that the normal allocation and the tiered allocation are |
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independent, and both start from the initial cluster state; as such, |
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the instance count for these two modes are not related one to |
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another. |
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|
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-v, --verbose |
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Increase the output verbosity. Each usage of this option will |
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increase the verbosity (currently more than 2 doesn't make sense) |
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from the default of one. |
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|
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-q, --quiet |
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Decrease the output verbosity. Each usage of this option will |
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decrease the verbosity (less than zero doesn't make sense) from the |
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default of one. |
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|
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-V, --version |
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Just show the program version and exit. |
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|
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UNITS |
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~~~~~ |
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|
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By default, all unit-accepting options use mebibytes. Using the |
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lower-case letters of *m*, *g* and *t* (or their longer equivalents of |
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*mib*, *gib*, *tib*, for which case doesn't matter) explicit binary |
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units can be selected. Units in the SI system can be selected using the |
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upper-case letters of *M*, *G* and *T* (or their longer equivalents of |
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*MB*, *GB*, *TB*, for which case doesn't matter). |
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|
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More details about the difference between the SI and binary systems can |
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be read in the *units(7)* man page. |
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|
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EXIT STATUS |
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----------- |
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|
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The exist status of the command will be zero, unless for some reason |
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the algorithm fatally failed (e.g. wrong node or instance data). |
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|
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BUGS |
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---- |
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|
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The algorithm is highly dependent on the number of nodes; its runtime |
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grows exponentially with this number, and as such is impractical for |
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really big clusters. |
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|
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The algorithm doesn't rebalance the cluster or try to get the optimal |
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fit; it just allocates in the best place for the current step, without |
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taking into consideration the impact on future placements. |
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|
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.. vim: set textwidth=72 : |
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.. Local Variables: |
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.. mode: rst |
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.. fill-column: 72 |
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.. End: |