This is the second blog in my series on Wan Optimization and Distributed Storage.
Remote Copy provides a powerful and flexible method for reproducing data and keeping that replicated data available for disaster recovery, business continuance, backup and recovery, data migration and data mining. For example in figure 1 the accounting department in Chicago runs a corporate accounting application and stores the resulting data. The designated backup site is in San Francisco. Nightly at 11:00 p.m., accounting updates are copied to the San Francisco facility using Remote Copy. Remote copying follows a three-step process.

1. Creation of a primary snapshot at the Chicago facility – this is called the primary snapshot, 2. Creation of a remote volume at the San Francisco office. Then you create a remote copy of the primary snapshot to the remote volume. 3. The system then copies data from the primary snapshot to the remote snapshot.

So, you ask “what is a snapshot?” A storage snapshot is a set of reference markers, or pointers to data stored on a storage area network (SAN). A snapshot is something like a detailed table of contents, but it is treated as a complete data backup.There are two types of snapshots – the first being the copy-on-write which creates a snapshot of changes to existing data every time the data is modified or new data is added to the volume. The second is split-mirror which creates a snapshot of all the existing data including the new and updated data. Copy-on-write involves the transfer of less amounts of data than the split-mirror method.

In a typical Distributed Storage environment Copy-on-write snapshots are scheduled for daily or weekly copies from primary to remote sites. These snapshots transfer data over a Wide Area Network and by utilizing Wanscaler Wan Optimization devices at both sites these data transfers are accelerated the time of complete transfer of the data is greatly reduced. In my next blog I will demonstrate Remote Copying within a Distributed Storage environment both with and without Wan Optimization to show the dramatic decrease in transfer times. 

In my next blog I will demonstrate remote copying and snapshots both with and without Wan Optimization via a video capture highlighting the results.