Scope: Backblaze Computer Backup (Personal Backup help articles), not B2 Cloud Storage. Checked October 3, 2026 (15:03 KST) against Backblaze’s own help center; links at the end. We have not installed, backed up to or restored from Backblaze for this article, and nothing here describes your account.
Short answer: Backblaze says it will back up "virtually any USB-connected hard drive," subject to the drive conditions listed below. But "supported" doesn’t tell you how long a disconnected drive’s data is kept. That depends on the Version History setting chosen for that computer, and the restore view you see today can hide data that is still retained. Backblaze says that "By default, Backblaze keeps a 30-day Version History of your files," and that "The retention selection is per computer."
Your fill-in worksheet
Fill this in from your own Backblaze account and computer. Leave a cell UNKNOWN until you have seen it yourself. Don’t write passwords, encryption keys or payment details here.
| Check | Where to look | Your entry |
|---|---|---|
| Drive selected for backup | Backblaze Settings → Select Hard Drives for Backup | UNKNOWN |
| Version History for this computer (30 days / 1 year / Forever) | Overview page of your account, per computer | UNKNOWN |
| Last time the drive was connected | Your own records, or the dates of any missing-drive emails | UNKNOWN |
| Date you last saw the drive’s files in your backup | Sign in → View/Restore Files | UNKNOWN |
| Date the restore view is set to | View/Restore Files → "To" drop-down | UNKNOWN |
Version History settings and what they mean for an external drive
| Setting | What Backblaze documents | Caveat | Official reference |
|---|---|---|---|
| 30 days (default) | Drives are kept if you "re-attach the hard drive at least once every 30 days." Otherwise "Backblaze interprets this as data that has been permanently deleted and securely deletes the copy from the Backblaze datacenter." | Backblaze emails alerts "When a drive is missing for 14, 21, and 28 days." | Backing up External Hard Drives |
| 1 year or Forever (selected extended history) | The 30-day reconnect-and-delete rule above does not apply: "users that have upgraded to either of our extended Version History options would not be subject to these restrictions." Instead, from the point it is enabled, "it will start keeping everything until the point that you have chosen, this will include external drives." With 1 year, versions remain "for 1 year after being modified or deleted from your device." | Only "as long as the account remains in good standing." Requires "Backblaze version 7.0 or later." Forever is "an additional paid upgrade." It "can only be enabled by upgrading an existing license," not when buying your first license. | Setting Up Extended Version History; Version History FAQ |
| Increasing history after a loss | New retention applies from that point on. | "This option is not retroactive and will not bring back data that has already been removed from your online backup through the normal 30-day deletion." | Setting Up Extended Version History |
Retained isn’t the same as visible
Here is the part that confuses people. Backblaze’s note reads: "With Extended Version history, files removed over 30 days ago, or external drives disconnected for longer than 30 days will be retained on our servers; however, if files/drives have not been present for longer than 30 days they will not appear in your current backup view."
That note applies only with extended history. On the default 30-day setting, a drive detached for more than 30 days is treated as "permanently deleted," as the table above shows.
So with extended history, a drive that is missing from today’s view doesn’t show, on its own, that the data is gone. It also doesn’t prove the data is still there. To look at an earlier date, Backblaze tells you to "Leave the ‘From’ side on ‘Beginning of Time’ then set the ‘To’ side to a period of time when your external was connected and working." Its FAQ adds: "Changing the ‘To’ field will show your backup status as of that date and time."
If the drive reappears at an earlier date, you can try creating a restore from that point. If it doesn’t, check your Version History setting and how long the drive was disconnected before drawing a conclusion. Backblaze also advises: "If you have data loss or computer failure, we highly recommend creating a restore immediately."
Drive conditions worth knowing
- Direct connection only. A drive must be "Directly connected to the computer (USB, Firewire, Thunderbolt, eSATA, etc)."
- Readable and writable by the OS. A drive must be "Natively read/write accessible by the operating system."
- Not a Time Machine volume (macOS). "Backblaze will not back up any drive that contains Time Machine data on it."
- Not removable storage (Windows). A drive must "Not mount as a ‘removable storage device’, as many flash, SD card, CD, DVD, Bluray, and some external SSDs do."
- No NAS. "Network (NAS) drives, remotely mounted computers or volumes, or shared volumes do not get backed up."
- Renames need reselection. "If you change the name of your external hard drive, you will need to reselect it for online backup."
- Reconnecting isn’t instant. "it may take Backblaze 2 to 4 hours to schedule the files on the external drive to be scanned and backed up."
- Stopping payment. "If you stop paying for the Backblaze service, the data will be deleted from the account. This also includes external drives, when they are disconnected."
Limitations
This guide covers Backblaze’s published help text only. It doesn’t cover B2 Cloud Storage, Business group settings, current prices or how long a scan takes. We can’t confirm your account’s setting or say how long your data will be kept. Before relying on Backblaze for a drive you plan to disconnect, confirm the Version History setting on your Overview page and try restoring a sample file.
Sources (checked October 3, 2026, 15:03 KST)
- Backblaze Help, "Version History FAQ": https://help.backblaze.com/hc/en-us/articles/360035247494-Version-History-FAQ
- Backblaze Help, "Setting Up Extended Version History": https://help.backblaze.com/hc/en-us/articles/360036946513-Setting-Up-Extended-Version-History
- Backblaze Help, "Backing up External Hard Drives": https://help.backblaze.com/hc/en-us/articles/217665398-Backing-up-External-Hard-Drives
- Backblaze Help, "Restoring Data from Secondary or External Hard Drives": https://help.backblaze.com/hc/en-us/articles/217665878-Restoring-Data-from-Secondary-or-External-Hard-Drives
- Backblaze Help, "Does Backblaze support external hard drives?": https://help.backblaze.com/hc/en-us/articles/217664538-Does-Backblaze-support-external-hard-drives