Drive retention period policy

Content Software for File User Guide

Version

4.2.x

Audience

anonymous

Part Number

MK-HCSF000-03

The Drive Retention Period policy refers to the amount of time you want to keep a copy of the data on SSD that you previously offloaded/copied to the object storage via the Tiering Cue Policy described further below.

Consider a scenario of a 100 TB filesystem (total capacity), with 100 TB of SSD space . If the data Drive Retention Period policy is defined as 1 month and only 10 TB of data are written per month, it will probably be possible to maintain data from the last 10 months on the SSDs. On the other hand, if 200 TB of data is written per month, it will only be possible to maintain data from half of the month on the SSDs. Additionally, there is no guarantee that the data on the SSDs is the data written in the last 2 weeks of the month, which also depends on the Tiering Cue.

To further help describe this section, let us use an example where the Tiering Cue Policy described below is set to 1 day, and the Drive Retention Period is set to 3 days. After one day, the Content Software for File system offloads period 0’s data to the object store. Setting the Drive Retention Period to 3 days means leaving a copy of that data in Content Software for File Cache for three days, and after three days, it is removed from the Content Software for File Cache. The data is not gone, it is on the object store, and if an application or a user accesses that data, it is pulled back from the object store and placed back on the Content Software for File SSD tier where it is tagged again with a new Tiering Cue Policy Period.

Consequently, the drive retention period policy determines the resolution of the Content Software for File system release decisions. If it is set to 1 month and the SSD capacity is sufficient for 10 months of writing, then the first month will be kept on the SSDs.

Note: If the Content Software for File system cannot comply with the defined Retention Period, e.g., the SSD is full and data has not been released from the SSD to the object store, a Break-In Policy will occur. In such a situation, an event is received in the Content Software for File system event log, advising that the system has not succeeded in complying with the policy and that data has been automatically released from the SSD to the object store, before completion of the defined Retention Period. No data will be lost (since the data has been transferred to the object store), but slower performance may be experienced.

Note: If the data writing rate is always high and the Content Software for File system fails to successfully release the data to the object store, an Object Store Bottleneck will occur. If the bottleneck continues, this will also result in a Policy Violation event.