NEW_STREAM Directive

The NEW_STREAM directive is recognized only if Allow Multiple Data Streams is set for the policy. NEW_STREAM directives are ignored if Allow Multiple Data Streams is not set.

If this directive is used in a backup selections list, the first instance of it must be on the first line. If it appears on the first line, it can also appear elsewhere in the list.

The presence or absence of NEW_STREAM on the first line of the backup selections list determines whether the backup is performed in administrator-defined streaming or auto-discover streaming mode.

Administrator-defined Streaming Mode

If NEW_STREAM is on the first line of the backup selections list, the backup is performed in administrator-defined streaming mode and the following occurs:

• The backup is split into a separate stream at each point in the backup selections list where the NEW_STREAM directive occurs.
• All file paths between NEW_STREAM directives are in the same stream.
• The end of each stream is defined by the start of a new stream (that is, a NEW_STREAM directive).
• The last stream in the backup selections list is terminated by the end of the backup selections list.

---

  Note    In the following examples, we assume that each stream is from a separate physical device on the client. Multiple concurrent streams from a single physical device can adversely affect backup times because the heads must move back and forth between tracks containing files for the respective streams.

---

For example, consider the backup selections list below:

This backup selection list has two data streams.

• The NEW_STREAM at the top of the list invokes administrator-defined streaming and starts the first stream. This stream backs up /usr and /lib.
• The second NEW_STREAM starts a second data stream that backs up /home and /bin.

If you add a backup selections list entry as part of an existing stream, its first backup is according to the next schedule that is due for the policy. If the next backup due is an incremental, then only changed files are backed up. To ensure that a new entry gets a full backup the first time, add it to a new stream. NetBackup performs a full backup of new streams that are added to the backup selections list.

In the previous example, assume you add /var after /bin. If an incremental is due that evening, only changed files in /var are backed up. However, if you add a NEW_STREAM directive before /var, then NetBackup performs a full backup of all files in /var, regardless of when they were last changed.

Auto-discover Streaming Mode

Auto-discover streaming mode is invoked if NEW_STREAM is not the first line of the backup selections list and the list contains either the ALL_LOCAL_DRIVES directive or wildcards. In this mode, the backup selections list is sent to the client, which preprocesses the list and splits the backup into streams as follows:

• If the backup selections list contains the ALL_LOCAL_DRIVES directive, NetBackup backs up the entire client but splits each drive volume (Windows) or file system (UNIX) into its own backup stream. See ALL_LOCAL_DRIVES Directives.
• If wild cards are used, the expansion of the wild cards results in one stream per wild card expansion.

If the backup selections list contains neither the ALL_LOCAL_DRIVES directive nor wildcards, auto-discover mode is not used and preprocessing is done on the server rather than the client. In this case, each file path in the backup selections list becomes a separate stream.

Auto-discover streaming mode applies to:

• Standard and MS-Windows-NT policy types, except for NetWare clients.
• Clients that are running NetBackup 3.2 or later.

With auto-discover, the client determines how many streams are required by preprocessing the backup selections list before the backup begins. The first backup of the policy always includes preprocessing. However, preprocessing does not necessarily occur before every backup and whether it occurs depends on the preprocess interval.

Setting the Preprocess Interval for Auto-discovery

The preprocess interval applies only to auto-discover mode and specifies how often preprocessing occurs. When a schedule is due and auto-discovery is used, NetBackup checks whether the previous preprocessing session occurred within the preprocess interval:

• If yes, NetBackup does not run preprocessing on the client.
• If no, NetBackup runs preprocessing on the client and makes required changes to the streams.

If necessary, you can change the interval by using the bpconfig command. The default is four hours and is a good value for most sites that run daily backups. If the interval is too long or too short, the following can occur:

• Too long an interval can result in new streams not being added soon enough and backups can be missed. For example, assume the preprocess interval is set to four hours and a schedule has a frequency of less than four hours. Here, it is possible for a new stream to be omitted from the next backup because the preprocessing interval has not expired when the backup is due.
• Too short an interval can cause preprocessing to occur often enough to increase scheduling time to an unacceptable level. A short interval is most likely to be a problem when there are a large number of clients that the server must contact for preprocessing.

The form of the bpconfig command to use for changing the interval is:

/usr/openv/netbackup/bin/admincmd/bpconfig [-prep hours]

For example:

/usr/openv/netbackup/bin/admincmd/bpconfig -prep 12

You can set the preprocess interval for immediate preprocessing by specifying -prep 0. (Preprocessing occurs prior to every backup.) Specifying -prep -1 sets the preprocess interval to the default value of 4 hours.

The following example sets the preprocess interval to 12 hours. You can determine the current interval by using the bpconfig command with the -L option:

bpconfig -L

(output of the above command)

Example - Auto-Discover Streaming Mode

Assume the selection list has the following entries:

For this selection list, NetBackup generates:

• One stream for the /lib directory
• One stream for the /usr directory
• One stream for each subdirectory and file in the /home directory because of the wildcard (*)

If the /home directory has three subdirectories: tom, dick, and harry, but no files, NetBackup produces a separate stream for each subdirectory: /home/tom, /home/dick, and /home/harry. This is a total of five streams for the backup.

However, if the wildcard is removed from /home, as in the following, then auto-discover is not used.

In this mode, NetBackup generates only three streams, one for each of the directories in the list. Preprocessing is done on the server instead of the client.