Troubleshooting guide

Backup and Restore Functional Description
228 NetBackup Troubleshooting Guide - UNIX
For all three types of backup and archive operations, bpsched uses bpcd (client daemon)
to start the backup/restore manager (bpbrm). If the required storage unit attaches to the
master server, bpsched starts the backup/restore manager on the master server. If the
storage unit connects to a media server, bpsched starts the backup/restore manager on
the media server.
The backup/restore manager starts the appropriate Media Manager process (bptm for
tape or optical and bpdm for disk) and also starts the actual backup (or archive) by using
the client daemon (bpcd) to start the backup and archive program (bpbkar) on the client.
The bpbkar program:
◆ Sends information about files within the image to the backup/restore manager, which
directs the file information to the NetBackup file database.
◆ Transmits the backup image to the Media Manager process, bptm or bpdm. The bptm
or bpdm process forks a second process, which receives the image and stores it block
by block in shared memory. The original process then takes the image from shared
memory and directs it to the storage media.
◆ If the storage is tape or optical, bptm checks the NetBackup media database for a
suitable media ID (for example, the correct density and retention level). If it can’t
find one, it obtains a new media ID from the Media Manager volume daemon,
vmd. The bptm program includes the media ID in a tape request to the Media
Manager device daemon, ltid, which finds the physical media and causes it to
be mounted on an appropriate device. bptm also controls the spanning of
backups across multiple tapes, if required.
◆ If the storage media is disk, bpdm writes the images to the path configured in the
disk storage unit. The system disk manager controls the actual writing of data.
In the case of an archive, NetBackup deletes the files from the client disk after the files
have been successfully backed up.
For multiplexed backups, the process is essentially the same except that a separate bpbrm
and bptm process is created for each backup image being multiplexed onto the media.
NetBackup also allocates a separate set of shared memory blocks for each image. Figure 9
shows an example of multiplexing images from two clients. The other client and server
processes are the same as on Figure 8.