Spanning one backup across several discs in Burn by Zaweba
When a backup is bigger than one disc, Burn by Zaweba plans the discs, splits large files, asks for each disc and puts a restore index on every one.
Large photo libraries and project folders rarely fit on a single disc. Burn by Zaweba handles that without fuss: when a backup is bigger than one disc, it spreads it across as many as needed and keeps the set together so it can be restored in full.
You don't have to divide folders by hand or guess what fits where. The plan is made for you before the first disc goes in.
Planning the discs
Before burning, Burn works out how many discs the backup will take, based on the disc size in your backup set. That number is the first thing you want to know, because it tells you how many blanks to have ready and roughly how long the job will run.
If the number looks too high, it is a sign to review the set. Perhaps it includes kinds of file you can leave out, or perhaps a larger disc size would mean far fewer discs to keep.
Files bigger than a disc
Some files are simply too large for one disc, or too large to fit in the space left on the current one. Burn splits big files into numbered pieces and places them across discs. Each piece is fingerprinted before burning, just like a whole file, so every piece is checked once it is on the disc.
When you restore, Burn joins the pieces back together and checks the result, so the file you get back is the file you put in. You never need to reassemble anything yourself.
Feeding the discs
During the burn, Burn asks for each disc in turn with a plain message, for example Insert disc 2 of 4. Keep your blanks in a pile and swap them when asked. There is nothing else to decide along the way.
The discs are labelled as part of the set, Set 2 of 4 and so on, so their order is clear. After the backup, Burn also offers printable labels, one per disc, which is worth doing for a set of several discs.
The restore index on every disc
The detail that makes spanning safe is the restore index. Burn puts one on every disc of the set, so any disc can explain the whole backup. If you pick up disc 3 years later, on a different PC, Burn can read it and show you what the entire backup holds, then ask for the discs it needs to bring back what you choose.
This means you don't depend on a particular first disc or a separate catalogue file. Lose the paper label, grab any disc from the box, and the backup still describes itself.
Mistakes to avoid
Don't mix discs from different sets in one sleeve without labels. The index will sort out what belongs where, but your own filing will be faster if each set lives together.
Don't skip the check after burning on a long set. A single bad disc in a four disc set can spoil the files whose pieces it holds, and the check is the moment to find that out. If a disc fails, burn it again before moving on.
And keep the blanks consistent. Planning assumes the disc size in the set, so use discs of that size for every disc in the run.
Where spanning fits
Spanning is part of the Backup Assistant rather than a separate tool. It works the same way when you back up only the files changed since last time, and Restore from backup discs knows how to ask for each disc and join split files. For a single folder that fits on one disc, none of this shows: you get one disc and one check, and that is the end of it.
