Elastic Compute Service:Resource Advisor overview

Resource Reservation

Purchase resource reservations to ensure resources are available for your business needs. Resource reservations are classified into the following types:

• Elasticity assurances: suitable for irregular resource demand patterns. They provide guaranteed access to resources only for pay-as-you-go instances and can take effect immediately or at a specified time. See Elasticity Assurance.

• Capacity reservations: suitable for stable, high resource demands. They provide guaranteed access to resources for subscription and pay-as-you-go instances and can take effect immediately or at a specified time. See Immediate capacity reservation and Scheduled capacity reservation.

The following figure shows the classification of resource reservations.

Choose a resource reservation plan based on your usage scenario, resource type, and effective time.

Private Pool

The public pool consists of automatically scheduled resources shared by all users. Instances may fail to be created when public pool resources are insufficient. When you purchase a resource reservation, Alibaba Cloud reserves matching resources in a private pool for your exclusive use.

Purchase resource reservations to create private pools, then use the reserved resources to create instances. You can perform the following private pool operations:

• When purchasing an elasticity assurance or capacity reservation, configure private pool attributes:

  • Private pool type: open or targeted. Open private pools suit business that requires guaranteed resource provision. Use an open private pool by specifying its ID, matching tags, or letting the system select one. Targeted private pools suit critical business that requires dedicated reserved resources — you must specify the pool ID to use a targeted private pool.

  • Tag matching: Use open private pools based on tags.

    For example, you have a script that creates instances with specific tags for critical business. To guarantee resource provision, purchase an elasticity assurance or capacity reservation with the private pool type set to Open and add the same instance tags. Tag matching is automatically enabled for the associated open private pool. When the script runs, it automatically matches the open private pool, eliminating the need to modify the script and reducing O&M costs.

  See Create a resource reservation.

• When creating instances, specify the private pool to use:

  • Specify the ID of an open or targeted private pool.

  • Add tags to match the open private pool associated with an elasticity assurance or capacity reservation that has the same tags.

  • Set the private pool type to Open to let the system select an open private pool.

  See Use private pool capacity to create instances.

The following figure shows the workflow for creating and using private pools.

Alibaba Cloud maximizes private pool capacity utilization.

• When you purchase elasticity assurances or capacity reservations, Alibaba Cloud considers your existing instances when evaluating whether the current resource inventory can meet your needs.

  For example, you have 100 pay-as-you-go instances that you plan to release and recreate. If a capacity reservation purchase is denied due to insufficient resources, set the private pool type of your existing instances to Open. This makes them count as matchable resources, allowing you to purchase the capacity reservation.

• After a private pool is created, it automatically matches existing instances with matching attributes.

  Note

  Only private pools for pay-as-you-go instances can match existing instances. Private pools for subscription instances can only be used to create instances.

• If instances no longer match a private pool after attribute changes (such as instance type or operating system), the system rematches them to other private pools.

Private pool use cases:

• Resources allocated based on business types

  A system administrator creates multiple targeted private pools and assigns different pool IDs to O&M personnel and developers, ensuring separate resource pools for each team.

• Resources allocated for all business types

  A system administrator creates open private pools. O&M personnel and developers use the reserved resources to create instances. When private pool resources are exhausted, resources from the public pool are used.

• Resources allocated based on tags

  A system administrator creates open private pools with business-specific tags. Instances created with the same tags automatically match the corresponding private pools.

  Important

  Use the tag-based grouping feature for private pools with caution. When cloud resource inventory is low, this feature can prevent an instance from being removed from the private pool, resulting in incorrect available capacity display.

• Resources allocated exclusively to specific business

  A system administrator creates targeted private pools for specific business. When the reserved resources are exhausted, no more instances can be created.