HP StorageWorks 6000 HP StorageWorks VLS and D2D Solutions Guide (AG306-96028, - Page 163
Replication of Incremental Backups, The Replication Sequence
View all HP StorageWorks 6000 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 163 highlights
Figure 71 The Replication Sequence . 1. A backup is performed (and its metadata is stored in the database). 2. The new backup is compared to the previous versions and the unique data in the new backup is identified. 3. The source device performs space reclamation on the previous backups to eliminate the duplicate data, and concurrently the replication data (containing just the unique data and metadata) is transferred to the target device. 4. The replication data is reassembled into an intact backup combining the new unique data with the duplicate data already replicated from previous backups. 5. The target device performs space reclamation on the previous backups to eliminate the duplicate data. HP VLS backup systems with HP Accelerated deduplication allow only unique pieces of data to replicate across the WAN link. This efficiency in understanding precisely which data needs to replicate may result in bandwidth savings in excess of 90% compared to transmitting the full contents of a cartridge at the source site. In addition to the unique data transmitted, there is some overhead of data instructions that also needs to pass across the replication link. This is known as control data, and is estimated to be about 1% of the full backup size. The control data is optionally compressed before it is transmitted. There are also some variances in the amount of data replicated from database backups and file system backups because of the different deduplication algorithms used and differences with incremental backups. Replication of Incremental Backups Most database incremental backups consist of block level changes in the database, while most file level incremental backups consist of changes at a file level. Depending on your recovery point objective (RPO) requirements at the disaster recovery site, you may choose whether or not to replicate incrementals. With the current capacity-optimized comparison algorithms in the HP VLS, the amount of data replicated for file system incrementals is almost the entire size of the incremental itself. (In firmware version 3.3.0 or higher, differential backups will deduplicate against each other so the amount of data replicated is reduced to the size of incremental backups.) Database block-level incrementals will also always be replicated as the entire size of the incremental backup because the data is always unique. HP StorageWorks VLS and D2D Solutions Guide 163