Using Ingest Time or Last Access Time in ILM rules

You can use Ingest Time or Last Access Time as the reference time in an ILM rule. For example, you might want to leave objects that have been viewed in the last three months on local Storage Nodes, while moving objects that have not been viewed as recently to an off-site location. You can also use advanced filtering if you want an ILM rule to apply only to objects that were ingested or last accessed on a specific date.

About this task

Before using Last Access Time or Ingest Time in an ILM rule, read through the following information to understand how to best use Last Access Time as a reference time, and to understand the other tasks that you need to perform:

When using Last Access Time as a reference time in an ILM rule, be aware that changing the Last Access Time for an object does not trigger an immediate ILM evaluation. Instead, the object's placements are assessed and the object is moved as required when background ILM evaluates the object. This could take two weeks or more after the object is accessed.
Take this latency into account when creating ILM rules based on Last Access Time and avoid placements that use short time periods (less than one month).

When using Last Access Time as an advanced filter or as a reference time, you must enable last access time updates for S3 buckets.

Note: Last access time updates are always enabled for Swift containers, but are disabled by default for S3 buckets.

The table summarizes the behavior applied to all objects in the bucket when last access time is disabled or enabled.

Type of request	Behavior if last access time is disabled (default) Last access time updated?	Behavior if last access time is enabled Last access time updated?
Request to retrieve an object, its access control list, or its metadata	No	Yes
Request to update an object’s metadata	Yes	Yes
Request to copy an object from one bucket to another	No, for the source copy Yes, for the destination copy	Yes, for the source copy Yes, for the destination copy
Request to complete a multipart upload	Yes, for the assembled object	Yes, for the assembled object

When using Ingest Time or Last Access Time as an advanced filter, you must also convert the desired time and date to microseconds since Unix Epoch.

Steps

If you are using Ingest Time or Last Access Time as advanced filters, determine the UTC date and time you want to use in the filter.
You might need to convert from your local time zone to UTC.
Convert the UTC date and time to microseconds since Unix Epoch.
For example, use date from a Linux command prompt.
```
# date -d '2015-03-14 00:00:00 UTC' +%s000000
14262912000000
```
If you are using Last Access Time as an advanced filter or as a reference time, enable last access time updates on each S3 bucket specified in that rule.
You can use the Tenant Manager or the Tenant API to enable updates to last access time for S3 buckets. See the instructions for using tenant accounts.
Attention: Be aware that enabling last access time updates can reduce performance, especially in systems with small objects. The performance impact occurs because StorageGRID must update the objects with new timestamps every time the objects are retrieved.