HubStor Inc.

Overview of Seamless Stubbing and the Retrieval Service

The Retrieval Service is a Windows Server agent that must be deployed on all file servers front-ending the storage you plan to tier to the cloud with the 'seamless stubbing' option. With the Retrieval Service installed, connectors can be configured in the HubStor Connector Service that use the 'seamless stubbing' option. Any stub policies in such connectors will then generate seamless stubs that transparently retrieve for any application or user request to open the item. Seamless stub look like this:

You can identify a seamless stub in two ways:
  1. The file icon is slightly faded in appearance, and
  2. The size on disk is only a few bytes and shows as zero bytes.

NOTE: In a DFS configuration, all file servers should have the Retrieval Service installed. As well, in a failover site, file servers should have the Retrieval Service installed so that seamless stubs continue to work as expected in a failover scenario.

The Retrieval Service is exclusively used for seamless stubbing and performs the following functions:

  • Intercepts the 'file open' command to see if an item is a seamless stub.
  • If a requested item is a seamless stub, the Retrieval Service will try to retrieve it from its local cache. If not in the cache, it will download the item from HubStor and provide it in the request stream.
  • If a local cache setting is configured, any retrieved content will be temporarily kept in the cache for a configured time period to optimize any subsequent opens of the same items.
  • Cleans items from the local cache according to the retention setting.
NOTE: The Retrieval Service includes a feature whereby you can exclude certain applications/processes from triggering retrieval from your HubStor tenant. For example, file browsers, antivirus, backup, and other programs that enumerate files can cause performance issues if they make programmatic requests to open items since they will invoke seamless stubs to perform retrievals. To learn how to configure this setting, see HOW TO INSTALL AND CONFIGURE THE RETRIEVAL SERVICE.

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