The Tiering Cue defines the period of time to wait before the data is copied from the SSD and sent to the object store. It is typically used when it is expected that some of the data being written will be rewritten/modified/deleted in the short term.
The Content Software for File system integrates a rolling progress control with three rotating periods of 0, 1, and 2.
- Period 0: All data written is tagged as written in the current period.
- Period 1: The switch from 0 to 1 is according to the Tiering Cue policy.
- Period 2: Starts after the period of time defined in the Tiering Cue, triggering the transfer of data written in period 0 from the SSD to the object-store.
For example: Let us say your Tiering Cue Policy is set to 1 day. All data written within the first day is tagged for Period 0. After one day, and for the next day, the next set of data is tagged for Period 1, and the data written in the next day is tagged for Period 2. As Period 0 rolls around to be next, the data marked for Period 0 is then offloaded to the object store, and new data is then tagged for Period 0. When Period 1 rolls around to be next, it is time to offload the data tagged for Period 1 to the object store and so on.
One important caveat to mention is that in the above example, if none of the data is touched or modified during the time set for the Tiering Cue Policy, then all the data as described will offload to the object store as planned. But let’s say there is some data in Period 0 that was updated/modified, that data is pulled out of Period 0 and is then tagged with the current Period of data being written at the moment, let’s say that is Period 2. So now, that newly modified data will not get offloaded to the object store until it is Period 2’s time. This is true for any data modified residing in one of the 3 Period cycles. It will be removed from its original Period and placed into the current Period that is marking the active writes.