The second article describes the method NBD (Network Block Device) which uses some of the virtualization functionality. It is available in the un-encrypted flavour of just NBD or encrypted via the LAN usually termed as NBDSSL For further information about the best practices from a VMware perspective please follow this VMware KB 1035096:
The backup itself also happens via the local area network (LAN) but directly communicates with the ESXi server to create the backup. The process involved in this backup is the host daemon, hostd. As described in the previous example of Client Based Backups and the need to suspend reads and/or writes backups, the NBD method does not need this as all, since he I/O is bypassed through the FVP Bypass Framework. The following figure illustrates how a backup in NBD mode takes place.
Figure 1: NBD Backup
- Backup triggers the backup to the remote ESXi through the Local Area Network (LAN).
- The process upon which this vStorage API call dependents on is hostd.
- There is a possibility to create a VMware Snapshot which quiesces the I/O to the VM and makes the application crash –and in certain cases- application- consistent.
- The I/O flows through the FVP Bypass Framework.
- Data is transferred via LAN to the Backup Server and saved on a pre-configured device e.g. a Tape Library, Disk, cloud etc.