External Hard Drives

During installation, Backblaze backs up any USB or Firewire hard drive that you have attached to your computer. You can also add external hard drives to Backblaze Computer Backup.

To be selectable for backup, a given drive must:  

• Have native read and write access by the operating system (for example, some utilities allow New Technology File System (NTFS) drives to be read/write accessible on macOS systems. Drives mounted in this way may be selectable, but they are not supported. Backblaze highly recommends that you do not attempt to back up these volumes.)
• Directly connect to the computer (USB, Firewire, Thunderbolt, eSATA, and others).
• Not be a Time Machine backup volume (macOS only).
• Not be mounted as a removable storage device as many flash, SD card, CD, DVD, Blu-ray, and some external SSDs do (Windows only).
• Be in working condition.

Multiple External Hard Drives

To ensure that all drives correctly update, you must ensure that your external hard drives are plugged in simultaneously as much as possible.

If you have multiple external hard drives, ensure that each drive is correctly selected. For more information about connecting external hard drives, see Back Up External Hard Drives for your specific operating system.

Unplugged or Failed External Hard Drives

Backblaze recommends that you keep your external hard drives connected to your computer as frequently as possible. If an external hard drive is disconnected, Backblaze retains the backed-up data based on your Version History setting.

30-Day Version History

With the default 30-Day Version History, reconnect your external hard drive at least once every 30 days to ensure that the drive's backed-up data remains in your backup.

Backblaze sends missing-drive alerts after the drive has been disconnected for 14, 21, and 28 days.

If the drive remains disconnected for more than 30 days, Backblaze may remove the drive's backed-up data from the backup.

1-Year Extended Version History

With 1-Year Extended Version History, Backblaze retains the data from a disconnected external hard drive for up to one year. You do not need to reconnect the drive every 30 days to retain its backed-up data.

Backblaze sends missing-drive alerts after the drive has been disconnected for 30, 345, and 360 days.

If you reconnect the drive within the one-year retention period, Backblaze recognizes and deduplicates previously backed-up files. You do not need to upload the entire drive again.

For more information, see Set Up Extended Version History.

Renaming and Replacing an External Hard Drive

If you change the name of your external hard drive, you must reselect it for backup.

Backblaze detects any files that were uploaded. The software uses a process called "deduplication" in which files are digitally fingerprinted (checksummed) before they are sent to the server. When a file's fingerprint matches an already backed-up file, but you renamed or moved the file (including drive-to-drive), it is updated at the servers rather than retransmitted.