NetBackup™ for VMware Administrator's Guide
- Introduction
- Required tasks: overview
- Configuring RBAC roles for VMware administrators
- Notes and prerequisites
- VMware vSphere privileges
- Managing VMware servers
- About VMware discovery
- Add VMware servers
- Change resource limits for VMware resource types
- Configuring backup policies for VMware
- Backup options on the VMware tab
- Exclude disks tab
- Configuring a VMware Intelligent Policy
- About the Reuse VM selection query results option
- Use Accelerator to back up virtual machines
- Configuring protection plans for VMware
- Malware scan
- Instant access
- Instant rollback
- Continuous data protection
- Backing up virtual machines
- VM recovery
- VMware agentless restore
- Restoring Individual files and folders from VMware backups
- Using NetBackup to back up Cloud Director environments
- Recover VMware Cloud Director virtual machines
- Restore virtual machines with Instant Recovery
- Protecting VMs using hardware snapshots and replication
- Best practices and more information
- Troubleshooting VMware operations
- NetBackup logging for VMware
- Snapshot error encountered (status code 156)
- Appendix A. Configuring services for NFS on Windows
- About configuring services for NFS on Windows 2012 or 2016 (NetBackup for VMware)
- Appendix B. Backups of VMware raw devices (RDM)
Backup or restore job hangs
NetBackup may have exceeded the maximum number of allowed VMware NFC connections to the ESX server when it used the transport modes nbd or nbdssl. Note that NetBackup uses one NFC connection per virtual disk on the ESX or ESXi server.
If NetBackup is configured to access the ESX server directly (not through a vCenter or VirtualCenter server), fewer connections are allowed. The following are the maximum connections as set by VMware:
Table: VMware NFC connection limits for nbd or nbdssl transfers
ESX version | Type of access to the ESX server | Maximum NFC connections allowed |
---|---|---|
ESX 4 | Directly to ESX server | 9 |
ESX 4 | Through vCenter | 27 |
ESXi 4 | Directly to ESX server | 11 |
ESXi 4 | Through vCenter | 23 |
ESXi 5 | Directly to ESX server | The maximum total for all NFC connection buffers to an ESXi host is 32 MB |
ESXi 5 | Through vCenter | 52 |
Try a different transport type (such as SAN or hotadd). If a different transport type is not available and NetBackup accesses the ESX servers directly, set up access through a vCenter (or VirtualCenter) server. Use of a server increases the maximum number of allowed connections. For example: With 27 connections, NetBackup can access a virtual machine that has up to 27 disks, if the ESX 4 server is behind a vCenter server.
Note that the connection limits are per-host (that is, per vCenter or ESX server).
For example, assume the following environment:
An ESX 4.0 server with three virtual machines.
Each virtual machine has ten virtual disks.
The virtual machines are behind a vCenter 4.0 server.
For a simultaneous backup of the three virtual machines, NetBackup requires 30 NFC connections. With a limit of 27 NFC connections per vCenter server, any of the three backup jobs may hang.
These limits are described in the VMware Virtual Disk API Programming Guide:
VMware Virtual Disk API Programming Guide
See also the following section of the VMware vSphere 5 Documentation Center: