Sector-Level Disk Backup Strategies

Disk backup can be done in very many combinations of strategies and each strategy offers its own pros and cons.

How Disk Backup Works: A consistent view of the disk contents is obtained by VSS. VSS also ensures that services prepare for live backup and prepare their data structures on disk so that the resulting disk image is application-consistent as well as crash-consistent.

Important Note: VSS cannot ensure consistency of non-Windows partitions and disks and offline disks. For example, if you attach a physical disk directly into a VM, that disk cannot be backed up from the host; instead, it must be backed up from inside the VM.

Disk backup via disk copy: By setting up a live disk to disk copy task you can clone a physical disk to another and have it ready to boot or access when disaster strikes. You will have to use a disk of the same exact size or larger than the original. This strategy also works with RAID disks that may be implement using several disks combined. For example a three disk stripe array can be copied to a single disk with sufficient capacity. The clone can then be booted alone if the RAID fails.

Make sure your boot settings are configured to force booting from the “correct” disk. Once you have several bootable disks in the server, the BIOS might use the “wrong” one next time you boot.

Disk backup via virtual disk conversion: BackupChain can create a virtual disk (formats: VHD, VHDX, VMDK, and VDI) from a physical disk. You can use this strategy to create a bootable virtual disk that can be mounted to a virtual machine and booted at any time. VHDs and VHDX may be used to boot directly from if added to the Windows boot configuration via bcdedit.exe

Virtual to virtual disk backup: Say you have a VM running Hyper-V. On your backup server you have VMware Workstation. You can convert the Hyper-V VM live and without interruptions into a VMDK, which you store on your backup server. There you can boot the VMDK any time you want. BackupChain can convert any VM from and to Hyper-V, VirtualBox, VMware Workstation / Server, and Virtual PC in all combinations.

Virtual to physical (i.e. Disk restore): You can copy the contents of a virtual disk back to a physical disk and boot from it with a physical machine. By backing up your physical disks to virtual disks and restoring from virtual disk to physical, you have basically implemented a traditional backup scheme where the virtual disk is the backup medium.

Remote disk backup via copy: Mounted virtual disks are offered in Windows 7 and Server 2008 and later. You can mount VHDs that sit on a network share on your LAN somewhere. These virtual disks appear in Windows like a real physical drive. In BackupChain you can set up a task to copy the server’s disks to the mounted disks on a schedule. In case of a disaster, these VHDs can be mounted anywhere on the LAN as physical disks and you can access data from them directly. Alternatively you could attach these VHDs to a virtual machine and boot immediately.