Tape is the archival spine of a 3-2-1 setup, and a real air gap once the cartridge is on a shelf. This article explains how Hiberden's tape destination works, how cartridges are identified, and what actually ends up on the tape. The supported configuration is LTO-9 through an LTFS-capable drive.
LTFS: tape as a filesystem
Hiberden never talks to the drive over raw SCSI. It drives the vendor's LTFS tooling (the open Linear Tape File System) to mount the cartridge, then treats the mounted cartridge like any other filesystem: it writes files, reads them back, and verifies them. LTFS is what makes that possible, and it is also what keeps your tapes readable outside Hiberden.
Because the on-tape format is delegated entirely to LTFS, nothing in Hiberden is tied to a specific drive generation. LTO-9 is the configuration we claim, and we do not claim a tested generation matrix beyond it.
LTFS tooling on Windows
On Windows, the wired implementation is IBM's LTFS (Single Drive Edition). It is separate vendor software, not part of Hiberden, and it is only needed for a real tape drive: the built-in virtual tape drive is self-contained and needs no vendor software. Hiberden auto-detects IBM's LTFS in the standard install locations; if yours lives somewhere else, set a custom path in Settings > Tape.
A fresh LTFS install often leaves its Windows service stopped until a reboot. Hiberden detects that as its own distinct state and offers a one-click Start service on the LTFS install card in Settings > Tape. You never mount a cartridge yourself: Hiberden mounts it when it writes or restores, and if the drive is empty when a restore needs a cartridge, it says the cartridge is offline and leaves the copy's status alone; if a different cartridge is loaded, it ejects it and asks for the right one by its label. If the drive is not showing up at all, see Tape drive not detected.
Adding a tape destination
Pick "Tape (LTO)" when adding a destination. There is no path to configure: archives are written to the connected tape drive. Save & test asks LTFS which tape drives are attached and shows Connected when at least one is listed. It does not load or mount a cartridge, so an empty drive passes. On Linux, open-source LTFS cannot list drives, so the test reports "No tape drive detected" even for a drive that is set up correctly; see Tape drive not detected.
Cartridge identity: the volume label
Hiberden identifies a cartridge by its LTFS volume label. A blank, unlabeled cartridge is refused for writing, on purpose: if Hiberden wrote to an unlabeled cartridge, the segments on it could not be attributed back to that cartridge, and could not be found again on restore. Label the cartridge with mkltfs first, then Hiberden will accept it.
Spanning across cartridges
An archive too big for one cartridge is split across several. Hiberden prompts you to swap cartridges as each one fills, and every segment is re-read and re-hashed (SHA-256) as it is written. With a real drive, each cartridge is also unmounted, mounted again and re-read before it leaves the drive. A span can start on a partially used cartridge: Hiberden fills the remaining space, keeping 64 MiB of headroom for the LTFS index, before prompting for the next cartridge.
Each cartridge in the set carries its own sidecar recording its segment's offset, length, and hash, plus the volume label and ordinal; a chain manifest describes the whole set. Restoring a spanned archive works the same way in reverse: cartridge by cartridge, with swap prompts and per-segment hash verification.
The catalog knows what is on which cartridge
You should not have to mount a tape to find out what is on it. The catalog tracks each cartridge's capacity, used space, and contents, so "what is on tape X" and "which cartridges do I need for this restore" are answered from the catalog with nothing in the drive.
Restoring only some files from a tape copy works too. Tape cannot jump to one file, so Hiberden reads the whole archive from the cartridge, checks its SHA-256, and writes out only the files you ticked. Hiberden first copies the whole archive from the cartridge into this computer's temporary folder and checks it there, so that drive needs free space for the whole archive.
What actually lands on the tape
An archive on tape is a set of ordinary files at the root of the LTFS volume: the archive's TAR in a part file named <name>__<key>.part000, a small JSON sidecar beside it recording that part's offset, length and SHA-256, and a chain manifest, <name>__<key>.hiberden-chain.json, describing the set. On one cartridge, .part000 is the whole TAR, so any LTFS-capable system can mount the cartridge and open it with standard tools, no Hiberden required. An archive spanned across cartridges is its parts joined in order. The full layout, including spanned sets, is documented in On-tape format (LTFS and the JSON sidecar).
Evaluate without hardware
Writing an archive to a cartridge, re-reading and re-hashing it as it is written, and restoring it all run end to end against Hiberden's built-in virtual tape drive, which presents the mounted cartridge as a real drive letter on Windows and as a folder elsewhere. The virtual cartridge is a full-size LTO-9, so an evaluation archive lands on one cartridge and no cartridge swap is asked for. It is the easiest way to prove out your tape workflow, and your budget, before buying a drive.