While data deduplication reduces storage costs by reducing the storage footprint, there is a cost incurred during the restore processes. During the restoration of a deduplicated backup, NetVault SmartDisk has to reassemble the Chunks as it restores the data. This reassembly process, also called rehydration, lengthens the time to restore the data. Therefore, if the Recovery Time Objective (RTO) is important for a specific database, email, or file system, consider the trade-off between reducing storage costs and increasing RTO when you identify which data to deduplicate.
You can increase deduplication ratios by targeting backups from the same database, file system, or application to the same NetVault SmartDisk Instance. When a backup is deduplicated and a previous backup from the same database, file system, or application has already been deduplicated by the NetVault SmartDisk Instance, only the unique or new Chunks that did not exist in the previous backup have to be stored in the Chunk Store. If a previously deduplicated backup does not exist in the NetVault SmartDisk Instance, most of the backup is considered unique data; this issue increases the number of unique Chunks that have to be stored in the Chunk Store.
When targeting backups to NetVault SmartDisk Instances, deduplication ratios decline if backups are targeted to random NetVault SmartDisk Instances. Quest recommends that you target backups from the same database, file system, or application to the same NetVault SmartDisk Instance.
Three factors determine the number of NetVault SmartDisk Instances required. If any of these factors are true, you must deploy multiple NetVault SmartDisk Instances. To determine the total number of NetVault SmartDisk Instances required, perform the following calculations:
The maximum result for the three calculations determines the number of NetVault SmartDisk Instances that must be deployed. For example, if the Unique Data Size calculation and the Deduplication Rate indicates that only one NetVault SmartDisk Instance is required, but the Ingest Rate calculation indicates that two NetVault SmartDisk Instances are required, you must deploy two NetVault SmartDisk Instances.
The Unique Data Size is the amount of unique data that is stored inside the NetVault SmartDisk Instance. An additional NetVault SmartDisk Instance must be deployed for every 15 TB of unique data on a 64-bit operating system (OS) and for every 5 TB of unique data on a 32-bit operating system. Use the following calculation to determine the number of NetVault SmartDisk Instances based on the Unique Data Size:100 + (120) + (240) = 460 GB460/15360 =.029
Rounded Up to Next Whole Number = 1 NetVault SmartDisk Instance460/5120 =.089
Rounded Up to Next Whole Number = 1 NetVault SmartDisk Instance
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