Bring DBAs into the SAN era

You may not want DBAs poking around inside your fabric, but the more they understand about SANs, the better they'll be.

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The role of storage within IT organizations has changed dramatically over the years, as well as the job descriptions of those who manage storage. Like it or not, database administrators (DBAs) haven't escaped the turmoil as their roles in storage architecture, management and administration continue to broaden.

Today's DBA is one of the key protectors of the most valuable company asset--its data. With a growing amount of data moving from flat file systems to organized relational databases, the DBA's participation in database storage has never been more important. Understanding the storage environment and the options available on storage platforms will continue to become an increasingly important part of the DBA's job.

In the future, the DBA will be asked to take on even more storage responsibilities. Not only will the DBA be responsible for database storage, but will be held accountable for the database's performance, which is directly related to the optimal structure of the database and placement of data. This change in a DBA's responsibilities is mostly due to the change in organizational structures through the evolution of the company (see "Storage organizational structures").

Software tools
Database vendor tools: All the major database vendors have tools for their software platforms. In fact, this can be a significant factor in determining how the database is used. Oracle, Sybase, IBM, and others all try to make it easier for the DBA to manage the database, but fall short in the area of storage management.
Third-party database specialists: Third-party software companies are trying to fill the gap left by database vendors. Their goal is to extend the existing vendor platform by adding more features and functionality. These are typically smaller companies that move faster to accommodate niche end-user needs.
Hardware vendors: The latest entrants into the database software market are the storage hardware vendors. Their goal is to leverage the existing processing power of the storage subsystems to drive database optimization software. This software will eventually evolve into database-aware storage that alters its access methods and caching algorithms to match the needs of the database, i.e., the hardware will become database-aware. Some hardware vendors are further along this path than others.

The evolution of complexity in the storage environment--for example, storage area networks (SANs), network-attached storage (NAS) and SAN/NAS hybrids--is also changing the DBA's role within IT. There's no longer the simple server and captive storage structure in most environments. Going forward, DBAs must be aware of the fabric (whether Fibre Channel or Ethernet) and highly developed software features available on advanced storage subsystems. The end result is DBAs will be more closely integrated with the storage hardware and software decisions and ultimately will be responsible for looking for ways to leverage these new features for better database administration. To understand this further, let's look at the critical storage layers a DBA must interface with.

Storage layers 
The storage layers represent the interface DBAs use to build a database with the appropriate characteristics. Information flows from business needs to define application requirements. The DBA takes these requirements directly from the application programmers. From the bottom up, hardware sophistication provides a platform for the software options that need to be understood by the DBA. Let's look at each layer individually.

Lines of business. It's only common sense that the earlier the DBA knows and understands the direction of the company, the better prepared for future requests they'll be. This is best accomplished through formal communication with the lines of business. Whether it's through e-mail, phone calls or regular meetings, the DBA benefits from storage information gained at these planning sessions.

Application. From the lines of business, applications are constantly being created and changed. The communication between the application programmers and the DBAs is critical. Much like interfacing with the lines of business, the sooner the DBA can get involved in the application change/creation process, the better. Knowing the type of data, availability and performance requirements of the application helps the DBA plan their storage strategy.

Hardware. The last thing a DBA should have to worry about is hardware. But because storage can have such a dramatic effect on performance and availability, it should be on the mind of every DBA. The DBA doesn't need to know the detailed architecture of the storage subsystems, but it helps to know some key components such as cache, channel type, drive size and rotational speed. Once these components are known, the DBA can identify the class of storage that would best fit the database being created.

Storage software/options
When identifying storage software options, the DBA should be most concerned with performance and availability (See "Software tools" above). Software that increases performance--such as striping and other RAID techniques--should be implemented. Other storage software such as dynamic multipathing and channel load balancing can increase performance. Availability can be improved through mirroring software or advanced remote replication tools for disaster recovery.

If a DBA knows a new application is being created by a line of business and the application will be read-intensive, they can then request storage. Enterprise class storage using mirroring hardware is available. The informed DBA requests storage on this enterprise-class subsystem that also has the ability to pre-fetch sequential read requests into cache.

Storage organizational structures
Multitasked: Usually, this is found in smaller organizations where a single person handles multiple tasks. An application programmer may code and build their own databases, while a storage network person will handle everything from storage provisioning to tape backup. Two people handle the entire environment.
Stove-piped: Within the stove-piped model, personnel and functions are strictly segmented. For example, there will be an OS or systems person, a storage person, backup person, database person, etc. While it's beneficial to have a specialist for each area, the time spent on communication and managing all the pieces on a project can limit the effectiveness of this organizational structure.
Centralized: This type of organization is typically the most efficient. From a central location, one or more people are responsible for a specialized role within the enterprise. The centralized model provides a flexible structure without being stove-piped. The centralized organization also works well over a distributed environment. For example, a single operations center can control the major functions for local and remote sites. Only a minimal staff is needed at the remote sites for physical tasks such as loading/unloading tapes. The centralized organization is best suited for DBA information-sharing and limiting personnel redundancy.

Database storage tools
For every database, DBAs can choose among tools from the database vendor, independent third party tools or from hardware vendors to support the database.

Vendor tools. Just as a DBA's job has evolved over the years, database companies have paid much more attention to storage-related issues regarding their software. For example, with the latest release of Oracle, it's now possible to:

  • Monitor from the application to storage system
  • Manage database space more easily
  • Use self-tuning performance management

Third-party tools. The major third-party storage software companies are also broadening their database software offerings. Most are marketed as "Database Edition," denoting that the product is database-aware.

Many DBAs will find that they're already using software from companies such as Veritas and Computer Associates (CA). If that's the case, you should explore bundling your database software tools with an existing site license agreement to further leverage pricing or gain access to a tool that was not included in the budget.

Hardware tools. Some software from hardware vendors may not be directly apparent as being database storage tools, but with the correct applicability they can be extremely powerful.

For example, a third mirroring hardware option might be used to create a near real-time copy of an active database for read-only access. Other hardware vendor tools are more directly related to database tuning, and suggest changes within the storage network by monitoring the host and storage subsystem.

Different organization, different roles
Beyond tools lies the question of how DBAs and storage administrators work together within an overall IT structure. There are essentially three basic models for an IT organization (see "Storage organizational structures," this page), and each has its strengths and weaknesses.

While multitasked and stove-piped departments can work in certain settings, centralized, storage-centric organization are going to be the most efficient for many companies. The DBAs that manage the many tablespaces and indexes are all located in a central data center and are all in the same group. There they have access to storage architects and full-time storage management for guidance. While there's not a great deal of direct responsibility for storage for a DBA in this situation, the DBA associates closely with the storage group. The centralized, storage-centric software-focused environment will continue to be a more efficient DBA group than older models.

This was first published in March 2003

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