Accessing virtual machines from VMware ESXi datastores by Vembu Backup agent can be done using three modes – HotAdd, Direct SAN and Network transport modes (NBD & NBDSSL). These three modes are referred to as VMware Data Transport Modes. Based on agent installation and VMware environment, Vembu VMBackup client automatically chooses any one of following transport modes. This article will explain about these data transport modes and their working mechanism in detail.
HotAdd Transport Mode:
HotAdd Mode is a LAN free data transfer mode which attaches the virtual disk to the backup proxy. Vembu VMBackup uses VADP (VMware vStorage API for Data Protection) for backup and replication from ESXi Servers. The data volumes that consist of the virtual machines will be mounted to the backup proxy automatically for the proxy to access it as a local disk. In this data transport mode, backup will be completed quickly since the disks are mounted from the VMs which significantly reduces the overhead.
Direct San Transport Mode:
Direct SAN transport mode provides the fastest data transfer speed with limited resource utilisation. It effectively transfers the backup and recovery data when the virtual machine disks are stored on fibre channel SAN or iSCSI SAN storage devices. Vembu VMBackup Client directly reads the data which needs to be backed up from SAN and sends them to Vembu BDR Backup Server’s storage repositories. SAN transport mode requires Vembu VMBackup Agent to run on a physical machine.
Network Transport Mode (NBD AND NBDSSL):
NBD (Network Block Device) & NBDSSL (Secure NBD) transmits data over TCP/IP connection between the ESXi hosts and Vembu VMBackup Client. ESXi hosts reads and sends the VM data to Vembu VMBackup Client after which it will be sent to Vembu BDR Backup Server’s storage repositories. The data transfer speed will be lower than the other two modes and it is not a LAN free transport mode. NBDSSL is similar to NBD data transport mode, but data transfer between Vembu VMBackup and the ESXi hosts is encrypted in NBDSSL.
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