File and Block Based Replication - Sometimes You Need Both

Any type of business continuity software that a company uses has a catch: the first task after the software is installed is to create a full copy of the production data at the disaster recovery (DR) site. What options the business continuity software provides to copy the data to the DR site is of a primary concern to businesses since it impacts what data is copied, how much data is copied and what type of planning companies have to do ahead of time.

Of particular focus in this blog entry is InMage Systems' DR-Scout since it provides companies with two options to copy production data to the DR site. The DR-Scout's FX agent copies data at the file level which gives companies more granular control over what data they copy. For instance, a company may only need to copy a set of files or a specific directory of files on an application server to the DR site. Using the DR-Scout FX agent, the company can select the specific files or directories that it needs to copy to the DR site. This minimizes:

• The overhead needed on the server while the data is copied
• The amount of network bandwidth that is needed between the two sites
• The amount of storage capacity needed at the DR site to store the data.

The flip side of using DR-Scout's FX file-based agent is that it only copies those selected files or directories to the DR site, not all data on the application server. To ensure all data on the application server is copied to the DR site, the DR-Scout VX agent that copies data at the volume or block level is a better option. Using the VX agent, a company selects whatever server volumes it needs to replicate to the DR site and then the VX agent simply copies all of the data on that volume.

Using the VX agent it is easier to guarantee that all needed is copied since it copies all data on specific volumes to the DR site. This eliminates the need (and the risk) of trying to forecast or anticipate what files or directories a company may need at the remote site now or in the future to do a recovery that is required using the FX agent. Also, going forward after the initial copy completes, the VX agent continuously captures all changes to data on volumes that it is protecting while the FX agent only replicates files or directories on a scheduled basis.

The first task of implementing any business continuity software is creating an initial copy of the production data at the DR site. As part of that task, companies need to establish both what production data they need to copy to the DR site and if the data that is copied will be sufficient for them to recover their specific applications. Since companies may only have superficial knowledge of which approach (file or volume-based replication) will work best for their company, the fact that InMage Systems' DR-Scout provides both gives companies the flexibility of choosing the replication method that is most appropriate for their applications. In the next installment in this series, I'll take a closer look at what prep work companies need to do at their production and DR sites to prepare to implement business continuity in their environment.