What is on a recorded disc and why it takes more space
A disc from Sigelith Backup stands on its own. You can read, check and repair it without this program, on Windows, macOS and Linux. That is why it holds additional files next to yours.
What is on the disc
| On the disc | What it is |
|---|---|
| README.txt | A description of the disc in Polish, English and German: what is on it and how to read, check and repair it without the program. Start with this. |
| data | Your files, in the same layout as in the backup, in their ordinary form. They open on any computer. On an encrypted disc every file name ends in “.age”. |
| SHA256SUMS | A checksum for every file on the disc. It lets you check the disc without the program. |
| par2 | PAR2 recovery data. It rebuilds damaged parts of files, as long as there is not too much damage. |
| tools | The par2 program (and, on an encrypted disc, also the age program) for Windows, Linux and macOS, with source code and a description of the formats. This keeps the disc readable many years from now. |
| seal | The Sigelith seal: proof that these files already existed at the moment of the stamp, plus a proof for each file on its own. It is there only if the source of the disc has a seal. |
| catalog | A register of earlier discs: what is on them and where they are kept. |
| sigelith-disc.json | A description of the disc for programs. |
| DISC-KEY.age | Only on an encrypted disc: the disc key, encrypted with the disc password. |
The data folder may also contain:
- LONG-PATHS.tar: files whose names or paths are too long for the disc and for Windows, in a single archive with their full paths;
- .tar archives in place of folders with masses of small files: this way the disc holds more;
- parts of files larger than a disc (.001, .002 and so on): on the following discs of a set.
The README on the disc explains how to unpack or join them.
There is no format of this program on the disc. Before recording, the program decrypts files from an encrypted backup and joins files stored in parts, and checks each one against its checksum.
Why the disc takes more space than your files
- PAR2 recovery data: 15% of the disc data by default, adjustable in the wizard from 10 to 30%. More recovery data means a better chance of reading an old, scratched disc.
- Tools with source code: about 17 MB, and on an encrypted disc about 53 MB, because the age program is added.
- The seal and file proofs: usually little space. The exception is a backup version with a seal made before version 3.0 of the program. Such a seal can only be checked with the full version index, so the index of all files in the backup goes on the disc, including files that are not on it. For a large backup this can be several hundred MB. The wizard warns you about it on the “Disc plan” page.
- The disc file system (UDF): a few MB.
Example: 8.7 GB of files on an encrypted disc, with 15% recovery data, takes up about 10 GB.
How much exactly the disc will take, the wizard shows on the “Disc plan” page before it records anything.