HP StorageWorks 9000 HP StorageWorks 9000-series Virtual Library System User G - Page 126
How it Works, Getting Deduplication Running on the VLS, Considerations, Installing the Firmware
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NOTE: Deduplication takes place after the data has been processed to the backup tapes. Therefore, any data backed up to compression-enabled virtual tape drives (both software and hardware compression) is compressed before it is deduplicated. How it Works The following is an overview of the deduplication process. See the HP StorageWorks VLS and D2D solutions guide for more detailed information. 1. When a backup runs, a data grooming exercise is performed on the fly. Using meta-data attached by the backup application, data grooming maps the content or "objects" of the backup, and assembles a content database. This process has minimal performance impact. 2. After the scheduled backups have completed, the content database is used to "delta-difference" (compare) objects in current and previous backups from the same hosts. There are different levels of comparison. For example, files may be compared using a strong hashing function, while other objects may be compared at a byte level. 3. When duplicate data is found in an older backup, it is replaced by a pointer to the most recent copy of the same data. Because the most recent backup is a full version, you achieve the fastest possible restores. 4. Users can enable an optional, secondary integrity check of data - a byte-for-byte comparison between the deduplicated version with pointers and its original version. With this option, the original backup is only replaced upon successful completion of the comparison. 5. Space reclamation occurs when duplicate data from previous backups is removed from the disk. This can take some time, but results in previously consumed capacity being returned to a free pool on the device. Getting Deduplication Running on the VLS Considerations To make the most of the deduplication benefits, review these considerations before setting it up on your VLS system: • Virtual cartridge sizing - The system cannot deduplicate versions of a backup that are on the same cartridge; the versions are not deduplicated until a new version is written to a different virtual cartridge. Therefore, you want the cartridges to be sized big enough to contain an entire backup job and to prevent too many backup jobs from piling up on the same cartridge, but small enough that you are not wasting overall cartridge space. • Additional nodes - For systems with long backup windows, you may want to include additional nodes to speed up the post-processing deduplication. • Additional capacity - Because you must store two full backups before the delta-differencing begins, you may want to include additional disk capacity at least the size of the sum of the backups. Installing the Firmware The deduplication feature requires an upgrade to the VLS firmware version 3.0 or higher. Download the VLS Firmware and Quick Restore CD Image appropriate for your VLS system from the HP website, and burn it to a CD. Then follow the instructions for using the quick restore CD. 126 Deduplication