Database Placement
In our centralized database example, the initial server in each data center will support both Class C and class B applications. By restricting the database sizes and store sizes as depicted in the illustration in Figure 5, SLA recovery specifications can be guaranteed as long as you practice due diligence on spare equipment and server backup and restore procedures. If you want to allow 100 GB databases, just make sure you can meet your SLAs.
Clearly, the most elegant recovery solution is a “snapshot” utility within a SAN box. Several manufacturers have products that “stream” data within the SAN to provide nearly instant recovery. Unless you have one of these solutions, I doubt you could recover 100 GB in 4 hours. You need to plan for server failure and database corruption. Neither happen that often, but both do happen.
Figure 5: Sample Database Placement
The scenario in Figure 5 plans for a couple of fast DLT drives in library systems to handle the backup and recovery of the servers in the Data Center. We know we could back up (?) a 7 GB database in eight hours as well as roll back any transactions we pick up along the way. This becomes our agreed upon “comfort zone.”
We also have decided that four databases are a better balance than the five databases recommendation. Once you fill four storage groups or the need for a Class A application arises, more server equipment must be allocated.
Another important thing to remember is the number of disk arrays you will need to support your applications. Each storage group should have a dedicated drive for the database as well as the transaction logs.
Summary
Ultimately, it is up to you to determine where the application fits into the overall scheme of things. The two main points I want to emphasize are:
- Your embrace and support of applications will help ensure their success.
- Choose your databases and storage group configurations based on SLA requirements and not based on department, geography or magic eight-ball.
© Copyright ECMS, Inc., 2000
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