Considerations for multi-host backups
NetBackup recommends using up to four backup hosts for a single NAS volume.
If enough resources are not available on the backup hosts for stream distribution, then the backup job is queued until the hosts gain enough resources to start backup streams.
If a backup stream running on any backup host is canceled or suspended, then the backup streams running on all the backup hosts for that NAS volume are canceled or suspended.
If a backup stream running on any backup host fails due to an error, then the backup streams running on all the backup hosts for that NAS volume are terminated and the backup job goes into an incomplete state.
In a rolling upgrade scenario you can upgrade the primary server to 10.4, but the backup host pool contains media and clients that are still on the older version. Consider the following regarding this upgrade:
D-NAS backup runs as it ran in the version prior to NetBackup 10.4, using a single host.
If you upgrade one of the media servers to NetBackup 10.4, the D-NAS backups use the upgraded media server as the only host. Multi-host backups are not possible.
If you upgrade more than one media server and client to 10.4, the D-NAS backups use all the upgraded media servers or clients in the backup host pool.