If you want to capture a moment in time with a camera, you snap a picture. When you want to capture the data on your cluster at a moment in time with the EMC® Isilon® OneFS® operating system, you take a snapshot.

EMC Isilon SnapshotIQ™ is a licensed software module that lets you create new snapshots and manage snapshot schedules. In this blog post, you’ll learn about SnapshotIQ basics and best practices.

SnapshotIQ overview

A snapshot is taken at a directory-level. The snapshot maintains an image of data that existed in that directory at that moment when the snapshot was created, even if the data changes. Taking a snapshot is an instantaneous operation. Rather than create a redundant copy of the data blocks, snapshots use pointers to reference current blocks on the cluster. Because of this, snapshots do not consume additional disk space unless the data referenced by the snapshot is modified. If the files are modified, the snapshot stores read-only copies of the original blocks.

Image provided by Patrick Kreuch

Image provided by Patrick Kreuch

Snapshots are the foundation for data protection strategies in OneFS. Snapshots are also used by the EMC Isilon SyncIQ™ software module to replicate a consistent point-in-time image of a directory from one cluster to another.

Watch the following video, “Data Protection and Disaster Recovery with Isilon SnapshotIQ,” to learn how to manage snapshots with the SnapshotIQ module. EMC Isilon Senior Solutions Architect, Chris Klosterman, answers the following frequently asked questions:

  • What is a snapshot and why do I need it?
  • How does SnapshotIQ work?
  • Where does OneFS store snapshots?
  • What are some example schedules?
  • How is data restored?
  • When do OneFS snapshots expire and how is the snapshot space reclaimed?
  • Can I modify data in a snapshot?

SnapshotIQ best practices

You may find that working with a large number of snapshots can become challenging to manage. Consider the following best practices to improve snapshot management and avoid cluster performance degradation.

  • Do not create more than 1,000 snapshots of a single directory.
  • Consider the depth of the directory path when creating snapshots. If the path is too high on the directory tree, it will cost more cluster resources to modify data referenced by the snapshot. If the path is too deep, you may need to create more snapshot schedules, which can be difficult to manage.
  • Create an alias name for your snapshot schedules in the OneFS web administration interface. Use the alias name to help you look up the most recent snapshot generated from a schedule.
  • Do not disable the snapshot delete job in the OneFS Job Engine.

For additional best practices and details about SnapshotIQ, see the “Snapshots” section in the OneFS Administration Guide.

If you have questions or feedback about this blog or these videos, email isi.knowledge@emc.com. To provide documentation feedback or request new content, email isicontent@emc.com.

Kirsten Gantenbein

Kirsten Gantenbein

Principal Content Strategist at EMC Isilon Storage Division
Kirsten Gantenbein
Kirsten Gantenbein
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3 Comments

  1. Eugene says:

    Can you provide some examples / suggestions on how to handle deleting large data when snapshots are in place? For example I just deleted 30TB from our cluster and didn’t consider snapshots at all. Coincidentally a scheduled snapshot took place minutes later and all of a sudden I have a 30TB snapshot. I went ahead and deleted the snapshot because we have no need for this data but now I’m wondering about some of our longer term snapshot schedules and if we really need them. For example snapshots that are taken every few months or years can cause issues/surprises later on when all of a sudden they blow up to the large size of deleted data.

    • This is a great question, and a good topic for a future article. At the moment, I don’t have many examples, but I can point you to the “Best practices for creating snapshot schedules” section in the OneFS 7.1 Web Administration Guide. This section describes how to create schedules based on how you want to delete snapshots. For example, you can create schedules with the same duration period for all snapshots to make sure that the oldest snapshots of a directory are always deleted. Or you can create schedules with different durations to delete snapshots based on how often a file is modified. I hope this information helps. Another resource is the ECN Isilon Community: https://community.emc.com/community/products/isilon. You can search this community for discussions on this topic.

  2. Seth Leonard says:

    Can you describe briefly how a snapshot is viewed with regard to events?

    Is a service account connected with the actual task and therefore connected to the event?
    Further, does this event get collected and pushed for monitoring by 3rd party software?

    Thanks!

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