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.
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 tiering minimum cooling period is 2 days. You can modify the default setting for the tiering minimum cooling period with the -tiering-minimum-cooling-days parameter in the advanced privilege level of the volume create and volume modify commands. Valid values are 2 to 183 days using ONTAP 9.8 and later. If you are using a version of ONTAP earlier than 9.8, valid values are 2 to 63 days.
The default tiering minimum cooling period is 31 days and applies to the entire volume, for both the active file system and the Snapshot copies.
You can modify the default setting for the tiering minimum cooling period with the -tiering-minimum-cooling-days parameter in the advanced privilege level of the volume create and volume modify commands. Valid values are 2 to 183 days.
The tiering minimum cooling period does not apply because the data moves the cloud tier as soon as the tiering scan runs, and you cannot modify the setting.
The tiering minimum cooling period does not apply because the data never moves to the cloud tier, and you cannot modify the setting.
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.
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.
Moving blocks back to the performance tier is not allowed.
Volume reads are needed for the data to be moved back to the performance tier.
However, the tiering policy takes effect only when the volume is in a FabricPool-enabled aggregate.
If you specify a different tiering policy, then the volume uses the default tiering minimum cooling period for that policy. This is the case whether the destination is FabricPool or not.
Assuming that both the source and the destination are FabricPool-enabled aggregates, the following table summarizes the outcome of a volume move operation that involves policy changes related to auto:
When you move a volume that has a tiering policy of... | And you change the tiering policy with the move to... | Then after the volume move... |
---|---|---|
all | auto | All data is moved to the performance tier. |
snapshot-only, none, or auto | auto | Data blocks are moved to the same tier of the destination as they previously were on the source. |
auto or all | snapshot-only | All data is moved to the performance tier. |
auto | all | All user data is moved to the cloud tier. |
snapshot-only,auto or all | none | All data is kept at the performance tier. |
In releases earlier than ONTAP 9.8, a clone inherits the tiering policy from the parent except when the parent has the all tiering policy.
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 |
|