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Manual Chapter: Managing Deduplication
Manual Chapter
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Managing Deduplication

Overview: Symmetric data deduplication

Symmetric data deduplication reduces the amount of bandwidth consumed across a WAN link for repeated data transfers. This feature is available only with an Application Acceleration Manager™ (AAM™) license.

With data deduplication, the system performs pattern matching on the transmitted WAN data, rather than caching. If any part of the transmitted data has already been sent, the BIG-IP® system replaces the previously transmitted data with references. As data flows through the pair, each device records the byte patterns and builds a synchronized dictionary. If an identical pattern of bytes traverses the WAN more than once, the BIG-IP closest to the sender replaces the byte pattern with a reference to it, compressing the data. When the reference reaches the other side of the WAN, the remote BIG-IP device replaces the reference with the data, restoring the data to its original format.

Task Summary

Perform these tasks to manage symmetric data deduplication.

Task list

Enabling symmetric data deduplication

Ensure that you have licensed and provisioned Application Acceleration Manager™ (AAM™) on the BIG-IP® system.
Symmetric data deduplication (SDD) reduces the amount of bandwidth consumed across a WAN link. You can enable symmetric data deduplication on the iSession™ connection between the local endpoint and any remote endpoints. SDD is enabled by default when you provision AAM.
  1. On the Main tab, click Acceleration > Symmetric Optimization > Symmetric Deduplication .
  2. In the Maximum Number of Remote Endpoints field, type the number of BIG-IP systems that you expect to connect to this one.
    This number specifies the maximum number of remote endpoints that can have symmetric data deduplication enabled, and thus, share the available cache. Any added iSession remote endpoint that exceeds this number receives no cache for deduplication. If you select SSD v2 in the Codec field, the maximum supported is 8. If you select SSD v3, the set value is 128.
  3. For the Enable Symmetric Deduplication setting, select Yes.
  4. For the Mode setting, select the method of storage for symmetric data deduplication.
    Option Description
    Disk Specifies that iSession uses the disk, in addition to memory, for storing information used for optimization.
    Note: If you enable data storage on the disk, you must restart the datastor service from the command line using the command sequence bigstart restart datastor for the change to take effect.
    Memory Specifies that iSession uses only memory for storing information used for optimization.
    Note: This setting can provide benefits for higher speed links.
  5. For the Codec setting, select the SDD version.
    Option Description
    SDD v3 Supports a high spoke count, such as for connecting remote sites and for mesh topologies.
    SSD v2 Supports a topology with fewer than eight spokes, such as replicating data between data centers.
    For SDD to occur between iSession endpoints, you must select the same codec on both the local and remote BIG-IP systems.
  6. Click Update to save changes.
    Important: Updating any of these settings causes the deduplication cache to clear.
Symmetric data deduplication starts after an iSession connection is established with a remote endpoint that also has symmetric data deduplication enabled, provided that the number of remote endpoints does not exceed the value in the Maximum Number of Remote Endpoints field.
If you changed the Codec setting, the system applies the new setting to any new data flows. However, if you enabled or disabled SDD, you must then restart the BIG-IP from the command line using the command sequence bigstart restart.

Disabling symmetric data deduplication

You can disable symmetric data deduplication on the iSession™ connections between the local endpoint and any remote endpoint.
  1. On the Main tab, click Acceleration > Symmetric Optimization > Symmetric Deduplication .
  2. For the Enable Symmetric Deduplication setting, select No.
  3. Click Update to save the change.
  4. Restart the BIG-IP from the command line by typing bigstart restart.
Symmetric data deduplication stops on all iSession connections between the local endpoint and any remote endpoints, and the deduplication cache clears.

Clearing the deduplication cache

Under some circumstances, you might want to clear the deduplication cache. For example, if you are testing the performance of symmetric data deduplication, you might want to clear the cache before you start and reset statistics, to ensure accurate performance data. The cache does not accumulate stale content, as a web cache does. It is more like a dictionary used in compression. To optimize compression ratios, the system manages storage automatically .
  1. On the Main tab, click Acceleration > Symmetric Optimization > Remote Endpoints .
  2. In the Remote Endpoints List screen, select the check box next to the remote endpoint for which you want to clear the cache, and then click Clear Dedup Cache.
    Note: Make sure you select a check box. If you do not select a remote endpoint, the system does not clear any deduplication cache.
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