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A guide for integrators and their clients
The scalability of any RAID storage solution is its truest means of differentiation. But, when we think of scalability, we often only look at the ability to expand the physical capacity of the storage device. That narrow view is unrealistic, considering the challenges faced by IT managers in the enterprise data center of the 1990's. There is a real need for storage to scale on many different levels: capacity, shared storage services, multi-host connectivity, performance, data protection levels, management and business continuance planning.
In today's data center, enterprise architecture planning demands that storage solutions move beyond the simple level of data integrity (simple data protection and component redundancy) to the level of data quality (user-selectable multi-level protection, faster data access, data redundancy) and beyond, to true data continuity (customizable, multi-level, multi-site data availability). The ability to support scaling to full data continuity options elevates to a new level the requirements placed upon vendors who seek to provide enterprise-class storage solutions.
Capacity Scaling
What does it mean today to scale a disk array in terms of capacity? Is it enough to provide hardware that has the physical space to store between a few gigabytes and a terabyte or more of data before you have to buy another box? Not really - yet, that is how many would define a scalable storage solution. Affirmative answers to all of the following questions are required to ensure that cost-effective capacity scaling is offered by your storage vendor:
Are both 3.5" and 5.25" SCSI disk form factors supported?
Are new higher capacity disk drives supported as they become available on the market?
Can I swap out my current drives and replace them with higher capacity drives without additional software or hardware changes?
Can I add capacity one drive at a time (or do I need to add groups of drives each time I want to add capacity)?
Can additional capacity be added online, without disruption of service?
Scalable Host Platform Support Most vendors today support the connection of multiple, heterogeneous host platforms to their arrays, although the number of concurrent connections per physical unit will vary from vendor to vendor and by vendor model. All RAID vendors in the open systems market...