Avamar: Partial backup functionality and best practices for initial backups
Summary: This article discusses Avamar partial backups and how they behave.
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Instructions
What are partial backups in Avamar?
When is a partial backup created?
When a backup is terminated the avagent service sends a message to the Management Console (MC) service. This creates a partial backup.
If the backup or replication fails because of a network outage, the message does not reach the server, and there is no partial backup to preserve.
Partial backups are created when a backup is "gracefully" terminated. This occurs when the Avamar Administrator service has the opportunity to send a "cancel" message to the avagent.
Similarly, a replication job creates a partial backup if the replication job gracefully terminates the avtar session at the end of the replication window.
When is a partial backup NOT created?
If a backup is terminated abruptly, (for example by issuing a "kill -9" on the avtar process), or due to a network outage, the partial backup is not created.
How long are partial backups retained?
Partial backups are retained on the Avamar server for 7 days.
If the client backup completes, the chunks which belong to the partial backup become part of the completed backup.
Partial backups and "best practice" for initial backups over a Wide Area Network:
It is better to run a series of 20+ hour backups, and allow the jobs to terminate at the end of the window every day, rather than enabling overtime and allowing a job to run for several days.
This is because the risk of a network outage that causes everything to be lost, is far greater if the job runs to completion with overtime enabled.
As described in the document on the behavior of the client caches, the file cache flushes itself every 20 minutes, and can be used to quickly "catch up" each time the backup restarts.
In relation to "best practices", when performing an initial backup it is best (but manually intensive) to start with small datasets and grow the datasets each day.
If this is not practical, then schedule the client to perform a series of long daily backups until the initial backup is completed. Do NOT enable overtime.
Do I need to worry about partial backups?
Partial backup functionality should be transparent to an end user. There should be no need to manually micromanage the existence of partial backups on an Avamar grid.
Potential issues that are related to partial backups:
It is normal to encounter occasional client issues and for partial backups to be created on the system. Issues which have been encountered are listed below.
A customer tries to back up a client which is larger than Avamar can hold:
A large backup whose data, even when deduplicated, cannot fit on the Avamar system.
The backup may run until Avamar becomes full and cancels the backup.
If the cancellation is graceful, this results in a large partial backup on the system which has a 7-day expiry. Avamar would be read-only and unable to accept further backup data.
This is a rare scenario, but it can be corrected by opening a new service request and explaining the situation to Avamar support.
The support engineer will investigate the root cause of the problem and perform the necessary actions to make the grid read/write again.
Partial backups ensure that data chunks backed up by a client to the Avamar Server are captured, even if the backup fails.
The next backup can leverage the data captured during earlier backups and resume from where it left off. The same data does not need resending.
This is advantageous for first-time backups or remote clients which have slow network connections to the Avamar server.
The next backup can leverage the data captured during earlier backups and resume from where it left off. The same data does not need resending.
This is advantageous for first-time backups or remote clients which have slow network connections to the Avamar server.
When is a partial backup created?
When a backup is terminated the avagent service sends a message to the Management Console (MC) service. This creates a partial backup.
If the backup or replication fails because of a network outage, the message does not reach the server, and there is no partial backup to preserve.
Partial backups are created when a backup is "gracefully" terminated. This occurs when the Avamar Administrator service has the opportunity to send a "cancel" message to the avagent.
Similarly, a replication job creates a partial backup if the replication job gracefully terminates the avtar session at the end of the replication window.
When is a partial backup NOT created?
If a backup is terminated abruptly, (for example by issuing a "kill -9" on the avtar process), or due to a network outage, the partial backup is not created.
How long are partial backups retained?
Partial backups are retained on the Avamar server for 7 days.
If the client backup completes, the chunks which belong to the partial backup become part of the completed backup.
Partial backups and "best practice" for initial backups over a Wide Area Network:
It is better to run a series of 20+ hour backups, and allow the jobs to terminate at the end of the window every day, rather than enabling overtime and allowing a job to run for several days.
This is because the risk of a network outage that causes everything to be lost, is far greater if the job runs to completion with overtime enabled.
As described in the document on the behavior of the client caches, the file cache flushes itself every 20 minutes, and can be used to quickly "catch up" each time the backup restarts.
In relation to "best practices", when performing an initial backup it is best (but manually intensive) to start with small datasets and grow the datasets each day.
If this is not practical, then schedule the client to perform a series of long daily backups until the initial backup is completed. Do NOT enable overtime.
Do I need to worry about partial backups?
Partial backup functionality should be transparent to an end user. There should be no need to manually micromanage the existence of partial backups on an Avamar grid.
Potential issues that are related to partial backups:
It is normal to encounter occasional client issues and for partial backups to be created on the system. Issues which have been encountered are listed below.
A customer tries to back up a client which is larger than Avamar can hold:
A large backup whose data, even when deduplicated, cannot fit on the Avamar system.
The backup may run until Avamar becomes full and cancels the backup.
If the cancellation is graceful, this results in a large partial backup on the system which has a 7-day expiry. Avamar would be read-only and unable to accept further backup data.
This is a rare scenario, but it can be corrected by opening a new service request and explaining the situation to Avamar support.
The support engineer will investigate the root cause of the problem and perform the necessary actions to make the grid read/write again.
Additional Information
Note:
Also see Avamar - Best practices when backing up remote clients over a Wide Area Network (WAN)
- Partial backups cannot be switched off
- Partial backups cannot be restored
- Partial backups cannot be seen in the Avamar Administrator UI
- Partial backups cannot be removed by end users
- Partial backup retention is not configurable
Also see Avamar - Best practices when backing up remote clients over a Wide Area Network (WAN)
Affected Products
AvamarProducts
Avamar, Avamar Client, Avamar ServerArticle Properties
Article Number: 000023642
Article Type: How To
Last Modified: 08 Mar 2024
Version: 5
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