With new Microsoft® Exchange Server 2007 database features, can fully featured and highly available storage area network infrastructures be replaced with simpler direct-attached solutions? The answer is not straightforward. In fact, it has several dependencies, not all related to the price per gigabyte of a disk unit.
When studying the deployment of Exchange Server 2007, you must understand how storage is typically provisioned to your application servers. There are two different approaches:
- Storage is an infrastructure component, provided as a utility service to servers
- Storage is a server add-on
With Exchange Server 2007, some companies take an application-driven approach, favouring DAS components, while others take an infrastructure-driven approach, favouring a strictly standardised SAN infrastructure.
SAN technology SAN technology is the application of networking to storage infrastructures. It is designed to allow you to share storage assets between servers.
The benefits of SAN environments include:
- Infrastructure management, growth and scalability
- Backup and recovery with shared tape resources
- The ability to virtualise data across many independent physical devices
- Advanced management (copy, clone, mirror or replication) of volumes in the back-end environment at the storage array level. This often is done at a much greater efficiency than would be achieved at the host level.
- Pooled disk units that diminish unused space and improve space efficiency, such as dynamically growing or shrinking a storage LUN based on its host utilisation
- The ability to transport a particular SAN logical disk unit from one server to another and share storage components such as network fabrics, controllers and disk drives
- Increased availability with redundant paths and components. Each server can access a disk unit through more than one path, through redundant host bus adapters, network switches, interconnects or controllers.
- The ability to enable storage consolidation and implement centralised storage management
DAS technology DAS is storage units (disks) plugged directly into the server, so that the storage is entirely dedicated to the server. Disks can be hosted within the server chassis or in one or more extension shelves.
The benefits of DAS environments include:
- Storage units are isolated from other servers and dedicated to the I/O workload of the server. Because there is a direct connection between the server and the disk units, costs for the interconnect modules and infrastructure employed for providing storage capacity are lowered.
- DAS solutions are less complex than SAN infrastructures. There are fewer components involved between the application and the resulting data that will be stored on the disk plateau (typically, an internal RAID controller, a cable, a shelf and a disk). But there is no network switch, no HBA, no network or isolation from other servers.
Points to consider
- What is your SAN capability maturity?
- What are the performance requirements?
- Will you be deploying replication?
- What are the strategy and organisation dynamics?
- Have you looked at all of the cost considerations?
To learn more, read the complete white paper.
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