Backup Engine
App-consistent VSS. Or your restore won't work.
Coordinated VSS Writers for SQL Server, Exchange, Active Directory, Hyper-V VM. We freeze writers, snapshot at quiesce, release. The 3-state badge tells you what consistency level your last backup achieved.
Click to enlargeHow it works
The VSS handshake, every backup.
App-consistent uses VSS Writers to coordinate with the running app before the snapshot is taken — so the image on disk is a known-good state, not a frozen accident.
Quiesce → Freeze Writers → Snapshot → Thaw — coordinated on every backup.
Crash-consistent backups often don’t restore cleanly.
Crash-consistent backups (the default for most products) image disk state at a single moment without coordinating with running databases. A SQL or Exchange database backed up crash-consistent often won’t restore cleanly — you get a half-written transaction log, a non-quiesced page, or a corrupt mailbox store.
- SQL Server’s VSS Writer pauses log truncation
- Exchange’s VSS Writer freezes mailbox stores
- AD’s writer captures NTDS in known-good state
- Restore actually works
Click to enlargeThe 3-state badge
Know your consistency level.
Every backup is graded. The badge tells you — before recovery day — exactly what consistency level your last backup achieved.
App-Consistent
All required writers responded successfully. Restore is guaranteed-clean.
Partial
Some writers responded, some didn’t. Database may need a log replay on restore.
Crash-Consistent
No writers responded; pure disk snapshot. Acceptable for desktops, dangerous for databases.
Supported writers
Which tier ships which writer.
| Writer | Resilience tier | DR tier |
|---|---|---|
| SQL Server VSS | DR-Only $5/mo | Plus $59/yr |
| Exchange VSS | Standard $10/mo | Pro $119/yr |
| Active Directory (NTDS) | Standard $10/mo | Pro $119/yr |
| Hyper-V VM Writer | Standard $10/mo | Pro $119/yr |
| File System (default) | All tiers | All tiers |
Degrade gracefully. Alert clearly.
Sometimes a VSS Writer doesn’t respond — service stopped, app version bug, transient timeout. We don’t fail the backup; we degrade to Partial or Crash-Consistent and surface it in the badge. Plus tier sends an email alert when consistency drops, so you know before recovery day.
- A writer timeout never fails the whole backup
- Consistency drops are surfaced in the 3-state badge
- Plus tier emails you when consistency degrades
Click to enlargeCoordinated VSS. Real restores.
Freeze writers, snapshot at quiesce, release — so SQL, Exchange, AD, and Hyper-V actually come back.