To Err Is Human, to Snapshot Is Divine

Humans make mistakes. They accidentally delete files. They try something and it doesn’t work. They fall asleep on the keyboard. And It’s important to have technology that can help people recover from their mistakes. It’s even better if they can recover without having to admit to anyone else that they messed up.

For storage products, snapshots are a key to data protection. Admins and end users have the ability to restore old files while minimizing the capacity overhead required. With the release of Qumulo Core 2.5, storage administrators can take a nearly limitless amount of snapshots, helping to make sure your end user’s data can easily be recovered if needed.

How do snapshots on Qumulo Core work?

In order to keep old versions of files without unnecessary duplication, Qumulo uses a method called write out of place. With Qumulo Core 2.5, you get even greater data protection and the ability to recover quickly from mistakes. You can create fine-grained policies and take billions of snapshots with easy access via NFS and SMB. This has several benefits:

Snapshots can be taken instantaneously

  • No storage is consumed when a snapshot is taken
  • The number of snapshots you can take is nearly limitless
  • There is no performance penalty for taking a snapshot
  • There is little to no performance penalty for reading and writing data from the filesystem in the presence of snapshots.

To illustrate exactly how snapshots work on Qumulo Core 2.5, let’s look at a theoretical example. Let’s say you put a 4MB file on Qumulo Core and then take a snapshot. You still have just 4MB on disk. Then you modify some part of the file, 1MB of it. The new 1MB is written out of place, and associated with only the “live” version of the file. 3MB of the original 4MB of data is shared between both versions of the file. The total storage usage for this file is now 5MB.

How do you recover files?

Now let’s say the inevitable has happened, and some of your data has been accidentally deleted from your Qumulo. To recover files from a previously taken snapshot, you can navigate to a hidden directory within each share called .snapshot. Here you will see a list of directories, each corresponding to an individual snapshot. Opening one of those will present the entire share as it looked at the time the snapshot was taken. Single files or whole directories can be restored by copying them back into the live file system. And with that, you can reassure a nervous user that their data has returned to the filesystem, and they can get back to their work.

Continually improving snapshots

As with all Qumulo features, we took an iterative approach in building snapshots. As soon as we had something that was production-ready, we put it into customers’ hands to let them start using it to get early feedback. Now we are steadily adding functionality — making it easier to use, more efficient, and adding more visibility and analytics. Our embrace of agile development methodology has resulted in 24 rock-solid versions of our software per year. Each release is the product of over three-hundred builds, one-thousand code check-ins and five million automated tests. And with our SaaS subscription model, Qumulo users can take advantage of our rapid innovation, upgrading to each new build at no additional cost.

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