This article explains the configuration options available when you create and edit a pool.
When you create a pool, in order to control its size, you can set three parameters: minimum idle instances, maximum capacity, and idle instance auto termination.
The minimum number of instances the pool keeps idle. These instances do not terminate, regardless of the setting specified in Idle Instance Auto Termination. If a cluster consumes idle instances from the pool, Databricks provisions additional instances to maintain the minimum.
The maximum number of instances that the pool will provision. If set, this value constrains all instances (idle + used).
If a cluster using the pool requests more instances than this number during autoscaling,
the request will fail with an
This configuration is optional. Databricks recommend setting a value only in the following circumstances:
- You have an instance quota you must stay under.
- You want to protect one set of work from impacting another set of work. For example, suppose your instance quota is 100 and you have teams A and B that need to run jobs. You can create pool A with a max 50 and pool B with max 50 so that the two teams share the 100 quota fairly.
- You need to cap cost.
The time in minutes that instances above the value set in Minimum Idle Instances can be idle before being terminated by the pool.
A pool consists of both idle instances kept ready for new clusters and instances in use by running clusters. All of these instances are of the same instance provider type, selected when creating a pool.
A pool’s instance type cannot be edited. Clusters attached to a pool use the same instance type for the driver and worker nodes. Different families of instance types fit different use cases, such as memory-intensive or compute-intensive workloads.
Databricks always provides one year’s deprecation notice before ceasing support for an instance type.
You can speed up cluster launches by selecting a Databricks Runtime version to be loaded on idle instances in the pool. If a user selects that runtime when they create a cluster backed by the pool, that cluster will launch even more quickly than a pool-backed cluster that doesn’t use a preloaded Databricks Runtime version.
Setting this option to None slows down cluster launches, as it causes the Databricks Runtime version to download on demand to idle instances in the pool. When the cluster releases the instances in the pool, the Databricks Runtime version remains cached on those instances. The next cluster creation operation that uses the same Databricks Runtime version might benefit from this caching behavior, but it is not guaranteed.