Using Data Domain Mtree replication for DD Boost and Oracle RMAN

In an earlier post, I looked at using RMAN managed replication to make two copies of an RMAN backupset to two separate Data Domains.

In the post Replicating an RMAN Backupset with Data Domain and DD Boost I then restored the database from the secondary copy to demonstrate that RMAN managed replication could be a useful tool for DBAs to protect against data center failures.

In this example however, I am going to use Data Domain’s native Mtree replication instead of RMAN’s managed replication.

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Replicating an RMAN Backupset with Data Domain and DD Boost

In this post, we will replicate an RMAN backupsets using RMAN managed replication and DD Boost.

In an earlier post, I showed how it was possible to use Data Domain’s Mtree replication to ensure that your Oracle RMAN backups are safely replicated to a second backup appliance when using Data Domain as an NFS target.

Replicating the RMAN backupset is important to protect databases from failures that might affect a whole data center, such as prolonged power or network failures, or events such as a flood that might destroy infrastructure.

These scenarios are rare but should they occur, having the RMAN backups of our databases available at a second location can be the different between an organization surviving such an event, or not.

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4K Logical Block Size size fails on VMware ESX 5.5

With the rise of all-flash storage arrays, DBAs have been exploring the opportunity to use the native 4K sectors/4K logical block mode of flash drives.

Traditional spinning disk almost universally uses a 512-byte block, or in reality most arrays now use a 520-byte block with 8 bytes reserved for Data Integrity Field or DIF, but flash drives use a 4096-byte block instead, which many all-flash arrays now expose to the operating system if instructed to do so.

On an EMC XtremIO, the LUN block size may be selected at LUN creation time from the Logical Block Size drop-down.

LUN sector selection

Several popular operating systems including Windows Server 2012, Red Hat Enterprise Linux 6.0 and Solaris 11.1 support this new configuration.

The advantage is by writing 4K blocks, instead of 512-byte blocks, the all-flash array is not required to use a Read/Modify/Write shuffle to update 512 bytes with a 4K block. There are some modest performance benefits to doing this, but don’t expect anything radical in most cases.

However be aware that at present, with VMware ESX 5.5, the VMware hypervisor cannot work with LUNs that use a logical block size of 4K, even if they are presented as RDMs. If you try to attach native 4K LUNs to a guest OS as RDMs, the guest OS power-up will fail with:

38 (Function not implemented)

4K LUN fail

A VMware Knowledge Base article confirms this is expected behavior.

VMware Knowledge Base 2091600

When using VMware, be sure to specify Normal (512 LBs) from your XtremIO array.

Configuring DD Boost on Linux for Oracle RMAN

In this post, we are going to install the DD Boost module for Oracle RMAN.

In the previous post, Configuring DD Boost Replication for Oracle RMAN, we enabled DD Boost on the Data Domain and set up storage units that replicate automatically between sites.

In this post, we are going to install and configure the DD Boost for Oracle RMAN module so that our RMAN backups can leverage the performance benefits of DD Boost.

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Configuring DD Boost Replication for Oracle RMAN

In this post, we are going to install the DD Boost module for Oracle RMAN.

DD Boost is an optional module that works with Data Domain and a number of applications and databases, including Oracle. DD Boost moves some of the sophisticated deduplication process from the Data Domain appliance to the database server, resulting in a dramatic reduction in network bandwidth and backup times.

A greater than fifty percent reduction in backup times for a full level zero RMAN backup is typical when switching to DD Boost although as always, your mileage may vary.

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