Why are there many SLP driven duplication jobs for 1 SLP that uses the same retention for the duplication jobs?

Article:TECH147430  |  Created: 2011-01-04  |  Updated: 2011-05-11  |  Article URL http://www.symantec.com/docs/TECH147430
Article Type
Technical Solution



Why are there many SLP driven duplication jobs for 1 SLP that uses the same retention for the duplication jobs?


If the backup source media is different, you will see in the nbstserv (oid = 226) log

add new batch job because "Media set does not match"


One objective of the nbstserv batching logic is to prevent media contention for tape operations (including VTL).



This parameter indicates how frequently nbstserv starts a duplication session. During a duplication session, NetBackup looks for completed backups on backup storage destinations and decides whether or not it is time to start a new duplication job.
Default: 5 minutes. Minimum: 1 minute.

This parameter indicates the size that the batch of images should reach before one duplication job is run for the entire batch.
The lifecycle does not request a duplication job until either:
The aggregate size of the images in a batch reaches the minimum size as indicated by MIN_GB_SIZE_PER_DUPLICATION_JOB
The MAX_MINUTES_TIL_FORCE_SMALL_DUPLICATION_JOB time passes. This parameter determines the maximum time be
tween batch requests.
Default: 7 gigabytes.

This parameter determines how large the batch of images is allowed to grow. When the size reaches the size as indicated by this parameter, no additional images are added to the batch.
Default: 25 gigabytes.

This parameter indicates how batches are created. The entry applies to the use of tape and disk.
0 = Select 0 to indicate that batches be created based on the storage lifecycle policy name.
1 = Select 1 to indicate that batches be created based on the duplication job priority from the storage lifecycle policy definition. This setting allows multiple storage lifecycle policies of the same priority together in a job.
Default: 1 (Use the storage lifecycle policy name).

This parameter indicates a value which serves as the multiplier for the number of concurrently active duplication jobs that can access a single storage unit. This parameter applies to tape media.
Storage unit configuration includes limiting the number of jobs that can access the resource at one time. (The Maximum concurrent write drives value.) This value specifies the optimal number of jobs that the Resource Broker can consider running on that resource.
This parameter helps administrators ensure a balance in the following situation:
To overload the Resource Broker with jobs that it can't run is not prudent.
Make sure that there's enough work that is queued so that the devices won't become idle. The TAPE_RESOURCE_MULTIPLIER entry lets administrators tune the amount of work that the Resource Broker can evaluate for a particular storage unit.
For example, a particular storage unit contains three write drives. If the TAPE_RESOURCE_MULTIPLIER parameter is set to two, then the limit on concurrently active jobs is six. Other duplication jobs requiring the storage unit remain queued.
Default: 2

Supplemental Materials


Online help:   NBU admin gui > Help > Help Topics > Search for "logic for batch creation"

Logic for batch creation
The Storage Lifecycle Manager service (nbstserv) is in charge of creating duplication jobs for storage lifecycle policies. Part of duplication job creation includes grouping the backup (or source) jobs into batches.

One objective of the batching logic is to prevent media contention for tape operations (including VTL).

Batching logic applies to both disk and tape. (Though the method to prevent media contention for disk is to use disk pools and then to limit I/O streams to disk pools.)

The batching logic requires that for each evaluation cycle, nbstserv consider all completed source jobs when determining which duplication job to run next. By default, nbstserv performs the evaluation once every 5 minutes.

nbstserv avoids overloading the Resource Broker (nbrb) queue with jobs. Too many jobs in the queue make the role of the Resource Broker harder and slows down system performance.

By default, nbstserv now creates groups based on the Duplication job priority setting of each storage lifecycle policy. Multiple storage lifecycle policies with the same priority can be batched together. Even if a NetBackup environment does not use the Duplication job priority setting, it benefits from allowing multiple storage lifecycle policies in one duplication job.

This batching logic change affects how duplication jobs appear in the Activity Monitor. Storage lifecycle policies that have been combined into one job appear under a single policy name: SLP_MultipleLifecycles. If a storage lifecycle policy has not been combined with another, the name appears in the Activity Monitor under the name of the SLP: SLP_name.

Users may see some duplication jobs that, although in the running state, are not duplicating data because they have no resources to read or write. These jobs continue to run until they receive resources to complete the job.
To turn off grouping by duplication job, change the DUPLICATION_GROUP_CRITERIA entry, a LIFECYCLE_PARAMETER.


Maximum concurrent write drives setting
The Maximum concurrent write drives setting specifies the number of tape drives that NetBackup can use at one time for jobs to this storage unit. The number of tape drives available is limited to the maximum number of tape drives in the storage device. If a job contains multiple copies, each copy applies toward the Maximum concurrent write drives count.
Select one number for the following:
Storage unit that contains only stand-alone tape drives.
Specify a number that is less than or equal to the number of tape drives that are in the storage unit.
Specify a number that is less than or equal to the number of tape drives that attach to the NetBackup media server for the storage unit.
Assume that you have two stand-alone drives of the same density and specify 1. Both tape drives are available to NetBackup but only one drive can be used for backups. The other tape drive is available for restores and other non-backup operations. (For example, to import, to verify, and to duplicate backups.)
 To specify a Maximum concurrent write drives setting of 0 disables the storage unit.

Duplication job priority setting
The Duplication job priority setting is the priority that duplication jobs have in relationship to all other jobs. In duplication jobs, NetBackup duplicates data from a backup destination to a duplication destination within a lifecycle. Range: 0 (default) to 99999 (highest priority).
For example, the Duplication job priority for a policy with a gold data classification may be set higher than for a policy with a silver data classification.
The priority of the backup job is set in the backup policy on the Attributes tab.

Article URL http://www.symantec.com/docs/TECH147430

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