Understanding FabricPool tiering policies

FabricPool tiering policies enable you to move data efficiently across tiers as data becomes hot or cold. Understanding the tiering policies helps you select the right policy that suits your storage management needs.

Types of FabricPool tiering policies

FabricPool tiering policies determine when or whether the user data blocks of a volume in FabricPool are moved to the cloud tier, based on the volume temperature of hot (active) or cold (inactive). The volume temperature increases when it is accessed frequently and decreases when it is not. Some tiering policies have an associated tiering minimum cooling period, which sets the time that user data in a volume of FabricPool must remain inactive for the data to be considered cold and moved to the cloud tier.

The FabricPool tiering policy is specified at the volume level. Four options are available:

The volume show command output shows the tiering policy of a volume. A volume that has never been used with FabricPool shows the none tiering policy in the output.

What happens when you modify the tiering policy of a volume in FabricPool

You can modify the tiering policy of a volume by performing a volume modify operation. You must understand how changing the tiering policy might affect how long it takes for data to become cold and be moved to the cloud tier.

What happens to the tiering policy when you move a volume

What happens to the tiering policy when you clone a volume

When you clone volumes, keep the following best practices in mind:
  • The -tiering-policy option and tiering-minimum-cooling-days option of the clone only controls the tiering behavior of blocks unique to the clone. Therefore, we recommend using tiering settings on the parent FlexVol that are either move the same amount of data or move less data than any of the clones
  • The cloud retrieval policy on the parent FlexVol should either move the same amount of data or should move more data than the retrieval policy of any of the clones

How tiering policies work with cloud migration

FabricPool cloud data retrieval is controlled by tiering policies that determine data retrieval from the cloud tier to performance tier based on the read pattern. Read patterns can be either sequential or random.

The following table lists the tiering policies and the cloud data retrieval rules for each policy.

Tiering policy Retrieval behavior
none Sequential and random reads
snapshot-only Sequential and random reads
auto Random reads
all No data retrieval

Starting in ONTAP 9.8, the cloud migration control cloud-retrieval-policy option overrides the default cloud migration or retrieval behavior controlled by the tiering policy.

The following table lists the supported cloud retrieval policies and their retrieval behavior.

Cloud retrieval policy Retrieval behavior
default Tiering policy decides what data should be pulled back, so there is no change to cloud data retrieval with default, cloud-retrieval-policy.

This policy is the default value for any volume regardless of the hosted aggregate type.

on-read All client-driven data read is pulled from cloud tier to performance tier.
never No client-driven data is pulled from cloud tier to performance tier
promote
  • For tiering policy none, all cloud data is pulled from the cloud tier to the performance tier
  • For tiering policy snapshot-only, AFS data is pulled.