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.
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.
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?
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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.