When a backup quote names a method, like incremental backup or differential backup, it’s telling you which copies have to be kept for a restore to work. Here’s what each method copies, and what each one needs to get a file back, using one week in a contractor’s estimate folder.
What each backup copies over one week
Backup quotes use three names for what gets copied. Microsoft’s page on Volume Shadow Copy backup types defines all three for backups made through VSS, a Windows feature that backup software uses. In plain words:
- A full backup copies everything in the folder. Restoring it takes only that one backup.
- An incremental backup copies only the files changed or added since the last backup, whether that was the full backup or the previous incremental. Each one holds just the changes since the one before.
- A differential backup copies every file changed or added since the last full backup and ignores the backups in between, so it gets bigger as changes pile up.
The file you’re actually protecting is the estimate open on the office computer. Your office revises it when a supplier price changes or a customer asks for a different scope, and your field crew may come back from a walkthrough with a note that belongs in it. Until a backup copies those edits, they exist only in that file, on that one computer.
Say your office keeps bids in one estimate folder on the office computer. On Monday the folder holds Estimate A and Estimate B, and a full backup copies the whole thing. On Tuesday someone edits Estimate A, Wednesday adds Estimate C, Thursday edits Estimate B, and on Friday nothing changes. Here’s what each method copies along the way:
What gets copied each day
Monday
- What changed
- Estimate A and Estimate B are in the folder
- Incremental backup copies
- Full backup of the whole folder, the starting point
- Differential backup copies
- Full backup of the whole folder, the starting point
Tuesday
- What changed
- Estimate A edited
- Incremental backup copies
- Estimate A
- Differential backup copies
- Estimate A
Wednesday
- What changed
- Estimate C added
- Incremental backup copies
- Estimate C
- Differential backup copies
- Estimate AEstimate C
Thursday
- What changed
- Estimate B edited
- Incremental backup copies
- Estimate B
- Differential backup copies
- Estimate AEstimate CEstimate B
Friday
- What changed
- Nothing changed
- Incremental backup copies
- Nothing new to copy
- Differential backup copies
- Estimate AEstimate CEstimate B
| Day | What changed | Incremental backup copies | Differential backup copies |
|---|---|---|---|
| Monday | Estimate A and Estimate B are in the folder | Full backup of the whole folder, the starting point | Full backup of the whole folder, the starting point |
| Tuesday | Estimate A edited | Estimate A | Estimate A |
| Wednesday | Estimate C added | Estimate C | Estimate AEstimate C |
| Thursday | Estimate B edited | Estimate B | Estimate AEstimate CEstimate B |
| Friday | Nothing changed | Nothing new to copy | Estimate AEstimate CEstimate B |
Keep this week in mind when you read a backup quote, starting with the bids you’d least like to redo from scratch. For the bigger picture, see our guide to data backup for contractors.
What you need to restore Thursday
Thursday is the day Estimate B changed. If the office computer won’t start that afternoon, the open file isn’t there to fall back on. The backups are your way back to that edit, and the two methods need different sets of them.
Monday’s full backup alone won’t do it. It’s a real copy of the folder, but from the start of the week: Estimate A and Estimate B as they stood on Monday, before Thursday’s edit.
With incremental backups, restoring Thursday takes Monday’s full backup plus Tuesday’s, Wednesday’s and Thursday’s incrementals: the folder as the week began, with each day’s change added on top. Every one of those copies has to be there. Wednesday’s can’t stand in for a missing Tuesday, because it only holds Wednesday’s change, so a missing day stays missing and the chain no longer reaches Thursday’s folder.
With differential backups, restoring Thursday takes just two copies: Monday’s full backup and Thursday’s differential. You don’t need Tuesday’s or Wednesday’s differential, because Thursday’s already includes every change since Monday.
What a Thursday restore needs
Full backup only
Monday’s full backup
Monday’s folder, without Thursday’s edit to Estimate B.
Incremental
Monday’s full backupTuesday’s incrementalWednesday’s incrementalThursday’s incremental
Every daily incremental since Monday, with none missing.
Differential
Monday’s full backupThursday’s differential
Tuesday’s and Wednesday’s differentials aren’t needed.
When the backup server builds the next full backup
Some backup products build a new full backup on their server from copies they already hold, instead of copying the whole folder again. AWS’s comparison of backup types calls this a synthetic full backup: the backup server combines the original full backup with the incrementals that followed to create the next full backup. AWS notes that it doesn’t save storage space, but it does save network bandwidth, because only the changes are sent to the server, not all your data.
The combining happens on the backup server, so there’s nothing for your office to do by hand, and not every product does it. If a quote mentions a synthetic or combined full backup, ask how that product handles it. Until that next full backup exists, a restore still needs the copies shown above.
Questions to ask about a backup quote
A method name on its own doesn’t tell you which copies have to exist to get Thursday’s file back. So bring the week to the quote and ask your provider:
- Which copies must still be available to restore Thursday’s file?
- What does each method name in the quote mean, in plain words?
- Does the product build a synthetic (combined) full backup?
- Which accounts are included?
Give them your estimate folder as the example, let them walk each method through it, and keep their answers with the quote. Don’t pick a method just because a page called it faster.
The accounts question matters more than it sounds. The office computer, the person who sends bids and the shared folder your field crew uses can be three different sign-ins, and a backup that covers one of them can leave the other two out. Get that list in writing before you count on it for a bid you can’t rebuild from memory.
How often backups should run is a separate question: see how often to back up a work computer. And making sure a restored estimate actually opens is what backup testing is for.
What Ghostworx covers
Ghostworx backs up the business data your coverage plan lists: usually business mailboxes and OneDrive or Google Drive files for covered accounts, plus the SharePoint sites or Google shared drives named at onboarding, kept separately from Microsoft or Google. Your quote states how often backups run and how long versions are kept. Files stored only on a computer, like the estimate folder in this example, aren’t part of the standard backup and are quoted separately. The full list is on our security and backup page.