Selecting storage for VM disks

Virtual machine (VM) disks are placed in the storage specified when creating the VM. If the storage is unavailable or full, the VM will not be created.

If the storage was not specified in the settings, the platform uses special tags to select the storage. Tags are set in VM configurations and settings of the cluster storages. When a VM is created, its disks get the tags set in the configuration. If the tag sets of disk and storage match, the disk will be placed in that storage. If a storage with the right tag set is not found, the VM will not be created.

Note

Tags are only used for VMs in clusters with KVM virtualization.

If neither storage nor tags were specified when creating a VM, the VM will be placed in the default cluster storage. If this storage is not specified, unavailable or full, the VM will not be created.

Using tags

Storage selection algorithm

To select the storage facility, the platform:

1. Forms a list of available storages, sorted in descending order of free space.
     Example: There are three storages connected to the cluster: SSD1 (25 GB free), SSD2 (10 GB free), SSD3 (400 GB free). A list will be formed:
   
   1. SSD3.
   2. SSD1.
   3. SSD2.

2. Sequentially, the platform will check storages from the list against the tags. The disk's tag set must be fully included in the storage's tag set. Examples:
   

   Disk tags	Storage tags	Result
   aaa	aaa, bbb	match
   aaa	bbb, ccc	no match
   —	aaa, bbb	match
   aaa	—	no match
   —	—	match
   aaa, bbb	aaa, ccc	no match

3. If the storage tags match the disk's tags and there is enough space in the storage, the platform places the disk in the storage.
4. If a storage with the right tag set is not found, the platform does not create a VM.

Managing tags

By default, nvme, hdd and ssd tags are created in the platform. These tags cannot be deleted. You can add your own tag when you create a configuration or connect a storage.

You can also manage tags via API requests:

• to get the list of tags, run the request

  GET https://domain.com/vm/v3/tag

  CODE

•  to create a tag, run the request

  POST https://domain.com/vm/v3/tag

  CODE

  with the parameter

  {
      "name": string,
      "note": string
  }

  CODE
   Comments

  name — tag name

  note — discretionary comment

•  to delete a tag, run the request

  DELETE https://domain.com/vm/v3/tag/<id>

  CODE
   Comments

  <id> —  tag ID