VM and Volume Allocators
Each Instance must be deployed in suitable deployment destination. Deployment destination is set of recommended resources that you can choose for deploying an instance. A deployment planner provides the suitable deployment destination that is required for a instance.
Allocators are used to figure out suitable host and storage pools for deploying the Instance:
VM Allocator
Volume Allocator
VM Allocator
VM allocator returns suitable hosts in the cluster where you can deploy the given instance. Various parameters e.g. CPU and RAM capacity, current state of the host are considered to decide the host.
VM allocator supports following algorithms to select a host in the cluster:
Algorithm |
Description |
|---|---|
random |
Selects a host in the cluster randomly. |
firstfit |
Selects the first available host in the cluster. |
userdispersing |
Selects the host running least instances for the account, aims to spread out the instances belonging to a single user account. |
userconcentratedpod_random |
Selects the host randomly aiming to keep all instances belonging to single user account in same pod. |
userconcentratedpod_firstfit |
Selects the first suitable host from a pod running most instances for the user. |
firstfitleastconsumed |
Selects the first host after sorting eligible hosts by least allocated resources (such as CPU or RAM). |
Use global configuration parameter: vm.allocation.algorithm to specify the algorithm that the Allocator must use. By default it is configured to use “random” algorithm.
Volme Allocator
VOlume allocator returns suitable storage pools available in the cluster where volumes of the given instance can be created. To decide the storage pools, it considers factors such as disk offering, storage capactiy, availability scope etc.
Volume allocator supports following algorithms to select a host in the cluster:
Algorithm |
Description |
|---|---|
random |
Selects a storage pool in the cluster randomly. |
firstfit |
Selects the first available storage pool in the cluster. |
userdispersing |
Selects the storage pool running least instances for the account, aims to spread out the instances belonging to a single user account. |
userconcentratedpod_random |
Selects the storage pool randomly aiming to keep all instances belonging to single user account in same pod. |
userconcentratedpod_firstfit |
Selects the first suitable pool from a pod running most instances for the user. |
firstfitleastconsumed |
Selects the first storage pool after sorting eligible pools by least allocated resources. |
Before 4.21.0, there was no named algorithm setting like vm.allocation.algorithm and volume allocator used to use the algorithm configured for VM allocator.
Since 4.21.0, dedicated named configuration is provided for user to configure volume allocation algorithm:
volume.allocation.algorithm: random (default)