Should I have two backup drives?

Having a good backup system is crucial for protecting your important files and data. While there are many different backup solutions available, one of the most common and effective approaches is using external hard drives for backup. A frequent question that arises is whether you should have a single backup drive or use two separate drives for redundancy. There are pros and cons to both approaches.

The benefits of a single external backup drive

Using just one external hard drive to back up your data has some advantages:

  • Simple and straightforward. Having a single designated backup drive makes the backup process easy to manage.
  • Less equipment required. You only need to purchase, connect, and maintain one drive.
  • Potentially lower cost. Depending on the storage capacity needed, a single drive may cost less than two separate drives.
  • Convenience. Storing and accessing backups from one location can be more convenient than managing two drives.

For some users, particularly those with smaller backup needs, a single external drive may provide adequate redundancy and protection for their important data. One drive with regular backup schedules and storage in a safe location, along with precautions like disk imaging, can be a viable backup solution.

Advantages of using two backup drives

While a single external drive can work for backups, having two separate backup drives provides some key advantages:

  • Redundancy. If one external drive fails or becomes corrupted, you still have another copy of your data on the second drive.
  • Rotation. You can alternate backing up to each drive according to a schedule (e.g. weekly, monthly) to have an on-site and off-site backup.
  • Expanded capacity. Two 1TB drives provides more total backup storage than a single 2TB drive.
  • Backup during drive replacement. If one drive needs to be replaced, you can continue backing up to the second drive in the meantime.
  • Peace of mind. Having two independent backup copies provides an extra level of protection from drive failure or data loss.

The main downside of having two drives is increased complexity and cost compared to a single drive setup. However, many users find the added redundancy and rotational backup capabilities worthwhile.

Backup drive capacity considerations

When deciding whether to use one or two external backup drives, a factor to consider is how much storage capacity you need. Here are some guidelines based on use cases:

  • Basic home computer: 500GB to 1TB capacity likely sufficient with one drive.
  • Average home user: 1TB to 3TB recommended for flexible storage with one or two drives.
  • Advanced home user: 3TB to 6TB provides good capacity for one or two drives.
  • Creative pro or power user: 6TB to 12TB gives room to grow with two drives.
  • Small business: Start with two 8TB drives for ample redundant storage.

Evaluate how much data you need to back up and your rate of data growth to choose one or two drives with suitable combined capacity.

Backup drive interface and speed

Along with capacity, the interface and speed of the backup drives are also important considerations:

  • USB 3.0 offers fast transfer speeds for quick backups.
  • USB-C is becoming more common for its versatility and speed.
  • Thunderbolt ports support excellent speeds for rapid backups.
  • Desktop hard drives use faster rotational speeds than portable drives.
  • SSD drives are much faster than traditional hard disk drives.

For your primary backup drive, choose a high performance option like an external SSD over a slower portable hard disk drive. This provides faster backup operations. The second backup drive can use a more economical traditional hard drive with USB 3.0 or Thunderbolt.

Example backup drive combinations

Here are some example combinations of one or two backup drives for different use cases:

Use Case Drive 1 Drive 2 (if applicable)
Basic home use 1TB portable HDD via USB 3.0 None
Advanced home use 2TB portable SSD via USB-C 4TB desktop HDD via USB 3.0
Small business backup 8TB desktop HDD via Thunderbolt 8TB desktop HDD via Thunderbolt

Tailor the combination to your specific needs – available ports, budget, and backup storage requirements.

Software considerations

The backup software you use is another key consideration when implementing a one or two drive backup solution:

  • Use imaging software like Apple Time Machine for complete system backups.
  • Sync software like FreeFileSync can mirror files between drives.
  • Cloud backup services like Backblaze provide an alternate backup target.
  • Backup software like Veeam helps automate and schedule backups.
  • Encryption software helps secure sensitive backup data.

The software should support your desired backup drive configuration and workflows. This helps streamline the backup process.

One or two drives for off-site protection

Storing a backup drive off-site (e.g. bank deposit box, office) provides protection against risks like fire, theft, and natural disaster. Some options for off-site backups include:

  • Periodically take the single drive off-site.
  • Use one of two drives for off-site rotation.
  • Have a third drive solely for off-site backups.
  • Supplement drives with cloud backup for off-site access.

An off-site backup provides an extra layer of protection for your irreplaceable data.

Cost comparison

While the cost difference depends on the specific drives selected, generally two backup drives will cost about 1.5 to 2 times the price of a single drive for a given total storage capacity:

Option Estimated Cost
1 external hard drive – 2TB $50 – $100
2 external hard drives – 2 x 1TB $75 – $150

However, the added redundancy and rotational backup capabilities are often worth the extra expense for many users.

Our recommendation

Overall, for comprehensive protection of critical data, we recommend using two external backup drives. This provides:

  • Redundancy if a single drive fails.
  • Ability to alternate backups to maintain on-site and off-site copies.
  • More flexibility to replace and upgrade drives one at a time.
  • Option to use different drive interfaces (USB, Thunderbolt, etc) for performance or compatibility.

For home users, an excellent combination is an SSD as the primary backup drive for speed, and a higher capacity traditional hard disk drive as the secondary backup target. This balances performance, capacity, and budget.

Using two external drives does require a little more effort than a single drive, both in initial setup and ongoing management. However, most users find that the extra confidence of having redundant on-site backups is worthwhile.

Backup tips for using two drives

To implement a smooth and effective backup strategy with two external drives, follow these tips:

  • Label the drives clearly as “Backup 1” and “Backup 2” to avoid confusion.
  • Use different colored cases to quickly distinguish the drives.
  • Alternate which drive is on-site vs. off-site on a weekly or monthly basis.
  • Schedule an automated backup routine to alternate between the two drives.
  • Store the off-site backup drive in a protected location like a bank safe deposit box.
  • Consider drive encryption to protect sensitive personal or business data.
  • Test restoring from both backup drives periodically to verify usability.

Putting in place procedures to use and maintain two separate backup drives takes a bit more diligence, but gives greater peace of mind knowing you have redundant copies of important files.

Potential downsides to two backup drives

While there are many advantages to using two external drives for backup, the approach does have some potential downsides to be aware of:

  • Increased cost compared to a single drive solution.
  • Requires more power and desk space for two drives.
  • Necessitates discipline to manually rotate drives on a schedule.
  • No protection against accidental file deletion or corruption if backed up to both drives.
  • More time consuming to set up and manage two drives instead of one.

However, with sound backup practices, the risks of dual drive downsides can be minimized compared to the much greater risk of losing data without a redundant backup.

Alternative backup options

Although two local external drives are recommended for most users, there are other backup alternatives to consider:

  • Single external drive – Lower cost but less redundancy. Requires more careful drive handling.
  • Cloud backup service – Provides off-site storage and accessibility but dependent on internet connection speeds.
  • External SSD drive – Faster transfers and rugged design but limited capacities and higher cost.
  • Internal drive – Convenient to access but less physical protection from system damage.
  • NAS device – Acts as a personal cloud device on local network but represents a single point of failure.

External hard disk or SSD drives tend to provide the best blend of capacity, performance, redundancy, and affordability for most home users backing up internally stored data.


Maintaining at least two separate external backup drives helps provide vital redundancy against drive failure, while also enabling rotational on-site/off-site backups. Alternating between drives offers more flexibility as drives age or fill up compared to relying on a single drive. And by using different interfaces, speeds, and capacities, you can balance cost, performance, and space based on use case.

Setting up and sticking to a routine with two backup destinations does require a bit more diligence. But most users find the extra peace of mind and data protection worth the small amount of additional effort. Utilizing dedicated backup software with support for multiple drives streamlines the process further.

For home users without a vast amount of data to protect, a single external HDD may be sufficient as long as proper care is taken and imaging backups are performed. But for most households and power users protecting treasured digital photos, videos, documents and more, two external backup drives provide inexpensive, redundant, and portable data protection that is hard to beat.