In this example we look at the Oracle data files’ consumed capacity reported from both the Oracle database (left-side bars in blue color) and the PowerMax storage system (right-side bars in green). When the Oracle database was created, the capacity of the data files was approximately 1.35 TB, reported by the Oracle database. Because the data_sg storage group (SG) had compression enabled, the storage it actually consumed was only 450 GB, reported by the PowerMax. This means a Data Reduction Ratio (DRR) of 3.1:1. Note that because in an Oracle database every data block has a unique header (regardless of its content), there are no deduplication benefits within a single database.
Figure 21. Example 1: PowerMax compression and deduplication of an Oracle database
We then created two SnapVX snapshots and linked (presented) them to another server. The snapshot creation and linking took only seconds. As a result, we had three copies of the original database, or approximately 4 TB (3 x 1.35 TB). When we inspected the storage, no capacity was added, resulting in a 9.3:1 DRR, because PowerMax snapshots only consume storage capacity when data is modified. We then deleted the snapshots.
Next, we created a database copy by using the RMAN DUPLICATE command. RMAN created a binary copy of the source database in a target database server and ASM disk group. Because RMAN used the network to make a full copy of the source database, the process took a few hours. After RMAN completed the database cloning operation, at a database level, we saw a 2.64 TB combined capacity of source and cloned databases. However, the storage capacity associated with the source and target storage groups was only 450 GB for a 6.0:1 DRR.
The reason for this result is because ASM Allocation Units (AU) are 4 MB with Oracle 12.2 and 1 MB with earlier releases. The PowerMax storage system, with 128 KB deduplication granularity, identified the cloned database extents as identical to the source and fully deduplicated them.
Finally, we created a second database copy using RMAN DUPLICATE command. Now, we had the source database and two copies for a total of 4 TB capacity at the database level. Again, the PowerMax storage system fully deduplicated the data and the storage capacity that was associated with the three databases remained 450 GB for a 9:1 DRR.