Cartridge and volume profiles¶

qicsilver uses two kinds of profile to read a tape. A cartridge profile names the physical cartridge. A volume profile says how the backup program that wrote the tape laid out its volume table and volumes. Both are TOML files that ship with qiclib. This page covers how they are chosen and how to see or force the choice. To write a new volume profile, see Writing a volume profile.

Neither is a drive profile. Drive profiles describe how a drive behaves on the bus and are used by tw; see Drive profiles.

Cartridge profiles¶

A cartridge profile describes one cartridge: its standard, track count, tape width and length, capacity, coercivity, and where known its model, vendor and label. The built-in profiles are:

For what each cartridge is, see Cartridges.

How a cartridge profile is chosen¶

The header segment records tracks per cartridge and segments per track. Those two numbers are fixed by the standard and the tape's length, so together they name the cartridge:

1. Only profiles with the header's track count are candidates.
2. If a candidate's standard fixes the segment count (QIC-40) and it matches exactly, that profile is chosen.
3. Otherwise each variable-length standard turns the segment count back into a tape length, using its own minimum-segments equation, and keeps the nearest cartridge if it lies within 10% of that length.
4. QIC-3010 and QIC-3020 use the same track counts. When both fit, a hint narrows the choice: the drive's tape status recorded in the captures, or header format code 6, which only QIC-3020 defines. With no hint, the report lists both.

You cannot force a cartridge profile. The choice only affects the cartridge line of the report; it does not change how the volumes are read.

See which cartridge profile matched¶

The cartridge line of qicsilver identify shows the result. With --json, the cartridge member holds the description, the matched catalogue entry (catalogue), the estimated length (estimated_ft), whether the match was exact (exact), and any alternatives.

Volume profiles¶

The QIC-80-MC standard fixes only bytes 0-56 of each 128-byte volume table (VTBL) record. Where the rest goes, how the volume's segments become bytes, and what catalog format the volume holds all depend on the backup program. A volume profile answers all three, one layer each:

A profile also carries a fingerprint ([match]): bytes the backup program wrote, such as MTN at VTBL byte 58. The built-in profiles are:

status says how far a profile has been exercised: spec (written from a standard), bench (confirmed on real tapes) or untested (written from a spec or another program's reader, never run on a tape here).

For the record layouts, see Volume table and the vendor pages for Colorado (CMS) and MTN.

How a volume profile is chosen¶

With --volume-profile guess, the default:

1. Fingerprint gate. Each profile's fingerprint is checked against every VTBL record. A profile whose fingerprint fails is eliminated for this tape. A fingerprint is something the software wrote, so a failure is final.
2. Scoring. Every surviving profile decodes every record, and the reading is scored with plausibility checks: does the segment range sit in the data area, is the date sane, is the label printable, is the compression code known, does the claimed size fit in the segments the volume occupies. Each check is worth +1 or -1. A wrong layout reads neighbouring fields as sizes and labels, and fails these checks badly, so the margin is usually wide.
3. Winner. The highest score wins. If the runner-up is within 2 points, the reading carries the low-confidence warning. If two profiles read the table identically, it carries vtbl-ambiguous. If two tie on score, the first is used and identify prints a note telling you to pick one.
4. Parser probe. When extract, inspect or tar builds a volume, the winner's file-set parser probes it. If the probe fails, the next profile that would have built the same bytes takes over.

A profile whose only fingerprint is in the volume bytes (qicstream-v2, novastor) cannot be confirmed from the volume table. It never wins the scoring. It is tried only when the winner's parser fails its probe.

If every profile is eliminated, the best-scoring reading is shown anyway, with a note that the volumes may be wrong.

Warnings¶

A reading's warnings appear in the identify report, in identify --json, in the inspect summary, in the TWVL header, in the tar's pax global header and in the damage report. The ones that come from the profile and its selection:

Other warnings describe the volume itself, for example directory-damaged, compression-unknown or spans-cartridges. The full list is in TWS-3 TWVL section 3.5.

See which volume profile matched¶

Run qicsilver identify. The volume profile line names the winner and its score, then every other profile's score, with eliminated after the ones whose fingerprint failed. The file set line names the parser. The warnings line follows when there are any.

To see why, add --raw. For each profile it prints every check with its points, ok or FAIL, and marks fingerprint checks [fingerprint]:

qicsilver identify --raw captures/NAME.twtz

After a volume is built, inspect shows the profile and parser that actually read it on its directory line, and the TWVL header records them.

Force a volume profile¶

Pass --volume-profile to identify, extract, inspect or tar (and to cinnabar). Give the same value to every command you run on the tape.

qicsilver identify --volume-profile mtn captures/NAME.twtz
qicsilver extract --volume-profile mtn captures/NAME.twtz captures/NAME-vols

The value is one of:

• A built-in name, such as cms-qic113. A misspelled name is an error that lists the built-in names.
• A path to a TOML file. A value is taken as a path when it ends in .toml, names a file that exists, is absolute, or contains a directory separator.
• guess, the default.

A forced profile is used even when its fingerprint does not match. identify then prints a note naming the checks that failed.

When no profile reads the tape correctly, override its layers by hand first (Manual read overrides), then keep what worked as a new TOML (Writing a volume profile).

See also¶

• qicsilver identify
• Manual read overrides
• Writing a volume profile
• Troubleshooting