Can Mirroring Replace Backups In Your Disaster Recovery Strategy?


TechTarget offers this definition of disk mirroring: “Also known as RAID 1, [disk mirroring] is the replication of data across two or more disks. The term ‘disk mirroring’ is sometimes used in a broader sense to describe any disk replication, but in most cases, it is meant within the context of RAID 1.

For context, in our recent post, “Understanding RAID Performance at Various Levels,” we explain the ins and outs of choosing a RAID level that’s right for your requirements. We also note that RAID 1 can, for the most part, be assumed to be a subset of RAID 10 because they are the same, except RAID only includes a single mirrored pair member.

Disk mirroring ensures you have at least one exact copy of your data at any given time in case of a drive failure, accidental deletion, or other data disaster. That raises the question: Can data mirroring replace backups in your disaster recovery strategy?

Disk Mirroring in Disaster Recovery

Mirroring brings with it some key advantages, including:

Real-time backup to an exact copy of all data, ensuring that the backup is always up to date and in sync with the primary data source.

High availability ensures that if one device fails, the data can still be accessed from an identical copy on separate devices.

Data integrity is maintained in mirrored backups that are exact replicas of your original data.

Disk Mirroring Drawbacks

While drive mirroring delivers these valuable benefits, it doesn’t protect you from all types of data loss — such as ransomware, a data breach, accidental deletion, or corruption — that is immediately mirrored in your backup copies. Mirroring is most effective as part of a comprehensive data protection strategy that includes a multilayered approach to backups and disaster recovery. Otherwise, you’re just asking for trouble.

Disk mirroring’s drawbacks include:

Added costs, especially for large data sets or where high-capacity storage devices are used, because mirroring requires at least double the storage capacity since every piece of data is stored on two or more devices. 

Potentially degraded system performance, depending on the implementation, because data must be written to multiple disks simultaneously for write operations, increasing the time required for these operations, especially if the disks aren’t co-located.

Limited threat protection because — while mirroring protects against hardware failures — it offers limited protection against data corruption, malware, and ransomware attacks. Data corrupted or encrypted by an attack is immediately mirrored to the other disks, so no ‘clean’ versions of the data are available.

Increased data management challenges, especially if you set up mirroring systems across different locations or in complex environments.

Limited recovery options for the reasons described above.

Expanded bandwidth requirements in environments where data is mirrored over a network — especially in distributed systems or cloud environments —can impact network performance for other applications and services. 

Mirroring and the 3-2-1-1 Backup Strategy

While mirroring is a sound strategy for high availability and other noted benefits, it’s no replacement for a sound backup strategy. That’s where the 3-2-1-1 backup strategy comes into play. It’s a proven approach to ensuring your data is protected and can always be recovered — even if your mirrored data is lost or corrupted.

The strategy is simple: Keep three copies of your data on two different media (tape or disk, for example), with one copy stored offsite (in a separate location or the cloud). The last “1” stands for immutability, where one copy of your backup is stored in a write-once-read-many-times (WORM) format that can’t be altered or deleted.

This strategy is a foolproof way to ensure you can recover from virtually any disaster

For expert help determining the data protection solutions for business, choose an Arcserve Technology Partner.

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