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Manual Chapter: Using Symmetric Data Deduplication
Manual Chapter
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The WAN Optimization Module uses symmetric data deduplication to reduce the amount of bandwidth consumed across a WAN link for repeated data transfers. This feature is available only with a licensed WAN Optimization Module.
The default settings are sufficient for a point-to-point deployment, such as data center to data center (DC-DC) replication. The procedure described is a global configuration for the WAN Optimization Module. You can adjust symmetric data deduplication for individual applications by creating custom iSession profiles, which you then apply to the virtual server that you are using for that type of application traffic. For information about customizing iSession profiles, see Customizing the iSession profile.
If you are configuring more than one pair of connected WAN Optimization Modules, you need to specify the number of remote endpoints you expect to configure. The WAN Optimization Module uses the information to divide the cache (disk or memory) it uses for symmetric data deduplication. The larger the number of remote endpoints, the smaller the amount of storage space that is allocated for deduplication. For additional details on deduplication cache, refer to Checking the size of deduplication cache.
To change the number of remote endpoints or disable symmetric data deduplication, use the procedure that follows.
1.
On the Main tab of the navigation pane, expand WAN Optimization and click Symmetric Deduplication.
2.
In the Maximum Number of Remote Endpoints box, type the number of WAN Optimization Modules you expect to connect to this one. The default value is 1.
Note: Changing this value clears the deduplication cache.
3.
For the Enable Symmetric Deduplication setting, specify whether to enable symmetric deduplication (Yes) or disable it (No).
4.
For Mode, select the appropriate setting:
Select Memory if you want deduplication cache stored in memory (faster access for high-speed networks, T3 or higher).
Select Disk if you want more space for deduplication cache.
Important: When you configure symmetric data deduplication, for DC-DC replication deployments, use the following guidelines:
Note: If you enable or disable data storage on the disk, you must then restart the datastor service from the command line using the command sequence bigstart restart datastor.
5.
Click Update if you have changed any settings.
Deduplication cache is where the system copies data that it has previously transferred. The cache on the local endpoint is kept in sync with the cache on the remote endpoint. If the same or similar information is requested again, the optimized version of the data can be sent instead of sending it all again.
BIG-IP® platform
What platform is the WAN Optimization Module running on? Memory and disk sizes vary for different hardware platforms, and this determines the maximum size that the system can reserve for deduplication cache.
Provisioning
What percentage of the system resources are allocated to the WAN Optimization Module? While minimal provisioning allocates fewer resources to WAN optimization, dedicated provisioning allocates more. If the module has more resources provisioned, more can be used for deduplication cache.
Disk or memory mode
Are you using disk or memory mode? The size of deduplication cache varies significantly, depending on whether you are storing it on disk or in memory.
Number of remote endpoints
What is the maximum number of remote endpoints configured on the system? The size of deduplication cache divided by the Maximum Number of Remote Endpoints value is the actual size of the deduplication cache that the WAN Optimization Module assigns to all local and remote endpoints. The deduplication cache size starts out the same on all of the endpoints.
Number of remote endpoints on the WAN Optimization Modules connected to this one
What is the maximum number of remote endpoints set on each of the remote endpoints? The local endpoint negotiates with each remote endpoint to determine the size of the deduplication cache, and the smallest amount is used for both endpoints.
For example, a company has a hub and spoke WAN Optimization Module configuration with four spokes, all using disk storage. The hub has 100 GB of disk storage, and each of the spokes has 50 GB disk storage. You could configure the hub as having 4 as the Maximum Number of Remote Endpoints value and the spokes each having 1. The WAN Optimization Modules negotiate, and they divide the 100 GB on the hub by the number of endpoints (4) and set the deduplication cache for each pair to 25 GB.
If any of the remote endpoints is not using deduplication, the local endpoint does not allocate any deduplication cache. The deduplication cache size is set to 0.
After the systems are up and running, the size of deduplication cache could change. For example, if a BIG-IP system has a disk drive failure, the Mode on that WAN Optimization Module automatically changes from Disk to Memory and the size is renegotiated.
On the Main tab of the navigation pane, expand WAN Optimization and click Remote Endpoints.
The Remote Endpoints screen opens. The SDD Cache (MB) column displays the deduplication cache size in megabytes for each remote endpoint.
1.
On the Main tab of the navigation pane, expand WAN Optimization and click Dashboard.
2.
In the Remote Endpoints panel, select any of the remote endpoints.
One of the values shown is Deduplication Cache, followed by the number of megabytes reserved for storing data.
Click the Clear Dedup Cache button on the remote endpoint. (The cache used between the two endpoints is cleared on both the local and remote endpoints.)
Under some circumstances, you may want to clear deduplication cache. For example, if you are testing the performance of symmetric data deduplication, you may want to clear the cache before you start and reset statistics to get accurate performance data. But typically, you do not want to clear the cache because it contains the data that the system has transferred before, and that will reduce the amount of time it takes to transfer similar data the next time.
You can use the Clear Dedup Cache button to clear the contents of the cache reserved for the remote endpoint on the system. The system communicates that the cache is cleared to the remote endpoint and the remote endpoint clears its cache as well. Therefore, you need only clear the cache on one of the WAN Optimization Modules in a pair, not both.
1.
On the Main tab of the navigation pane, expand WAN Optimization and click Remote Endpoints.
2.
Check the Select box next to the remote endpoints for which you want to clear the cache, and then click Clear Dedup Cache.
The system clears the cache it has reserved for the remote endpoint.
Note: Make sure you have checked a box. If you have not selected a remote endpoint, the system does not clear the deduplication cache.
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