Lorre Bumgardner

Snapshots, Clones and Mirrors Oh My – Unravelling the Mystery of When and Where to Use Them

It’s been said that those who rule data will rule the entire world.

And unquestionably, there are two assets that are the most valuable to organizations of all types and sizes; data and data protection. The ever-evolving landscape of cyber threats and availability of technology options like snapshots, clones and mirroring makes choosing the right fit a daunting task. Each has its place in a robust data protection architecture so it’s important to understand the benefits and trade-offs when creating your plan.

What Are Snapshots and Clones?

Snapshots and Clones are similar in that they both offer a cost effective means of data protection. Snapshots are point in time copies of a volume, data set or even a virtual machine. The full image is captured once and changes are captured in all snapshots that follow. This reduces the storage overhead required to store them which keeps the cost low. In many cases snapshots are stored locally, making them quickly accessible and a great tool to meet aggressive recovery time objectives (RTO). A couple of downsides to snapshots are that they don’t eliminate a single point of failure and may have a negative impact on application performance because they are reliant on the original data they’re of no use if that’s lost. Storing them locally for RTO purposes means that you would lose both the source data and the snapshot in the event of a hardware failure. On the performance front, since write operations are not allowed during the time snapshots are being created then end users may experience some latency.

And like snapshots, clones are point in time images. But the difference is that a clone is an exact image of either a volume or a logical unit. Clones can be created that are linked, which means they reference the original instance via a snapshot or full where the entire instance is copied. Clones share many of the upsides and downsides to snapshots – they can be quickly accessible and a great option to meet aggressive RTO’s and are cost effective in terms of the footprint required to store them. On the downside, a single point of failure may not be eliminated depending on the clone type and storage location, and performance in production environments can take a hit.

Advantages of Snapshots and Clones

  • Cost effective
  • Quick to access
  • Great for meeting aggressive RTO’s

Disadvantages of Snapshots and Clones

  • Dependent on healthy source data
  • If stored locally for RTO, hardware failure is catastrophic
  • Performance impact

Best Use Cases of Snapshots and Clones

  • Quick recovery of lost or corrupted files
  • Non-business critical datasets
  • Test and development environments

What is Mirroring?

Mirroring creates an exact replication of a disk or volume (e.g. mirror image). It can be carried out by either hardware, in the case of a storage array controller or software. It can also be done locally using RAID 1 in a multi-drive system or remotely by enabling replication either on the array controller or in software running on the server.

Synchronous mirroring generates two write operations – one on each system – and does not allow additional writes until both complete. Asynchronous mirroring generates two writes as well, but allows the primary system to continue writes, making the mirror slightly “behind” the primary. Like snapshots and clones, there are advantages and disadvantages to mirrors, but the primary benefit is for disaster recovery. If the original volume is lost or damaged, you have reasonably quick access to the exact same data, which is great for helping meet aggressive recovery point objectives (RPO). The downsides, however, are in both cost and performance – a mirrored configuration will basically double your hardware costs, and because each write is executed twice the performance may suffer. Additionally, replication solutions are typically proprietary, which means they don’t work in multi-vendor environments so you’re locked into your vendor of choice.

Advantages of Mirroring

  • Full, exact copy of original dataset
  • Remote mirroring separates location for disaster recovery purposes
  • Great for meeting aggressive RPO’s

Disadvantages of Mirroring

  • Cost – both hardware and software
  • Doesn’t protect against file corruption or accidental deletion
  • Vendor lock-in

Best Use Cases of Mirroring

  • Full recovery of all data
  • Business-critical data sets
  • Disaster Recovery solution

DataCore’s software-defined storage (SDS) provides a cost effective way to receive the benefits of all of these technologies, and more, with the freedom to choose the hardware that best meets YOUR needs not ours.

Click here to discover more about our SDS features and capabilities or if you’re ready to dive in then feel free to request a live demo today!

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