Vendor extensions¶

The QIC standards fix the recording, the header and the first 57 bytes of a volume table entry. Everything after that, and often the volume contents too, was decided by the backup program that wrote the tape. This section documents the vendor layouts Tapewyrm has read from real tapes.

Each layout here is encoded as a volume profile in packages/qiclib/qiclib/volume/profiles/. A profile answers three questions: which volume table fields sit where ([vtbl]), how wide the compression extent fields are ([extent]), and which parser reads the volume ([fileset]).

Layouts¶

Two more profiles, qicstream-v2 and novastor, were written from another project's reader source code and have never seen a real tape. They are listed on Volume table.

Adding a layout¶

When a tape reads as vendor-unknown or qic80-rev-n with warnings, its software has a layout of its own. To work it out:

1. Run qicsilver identify --json and look at the volume table record's raw_hex.
2. Look for a mark the software wrote in bytes 57–127: a signature, a name, a version word. That becomes the profile's [match].
3. Find the sizes and the label by their values: a directory size that fits the segments, a data size that fits the compression ratio, printable text.
4. Try the reading by hand with --vtbl-field, --extent-offset-bytes and --fileset-parser (Manual read overrides).
5. When it reads, write the profile (Writing a volume profile).

See also¶

• Volume table
• QIC-113 file sets
• Cartridge and volume profiles