A Windows 2000 RAID
If you have had the chance to experiment with Windows 2000, I imagine you’ve found some hidden, unhyped gem. After all, not every feature is going to receive the attention that has accompanied Active Directory. Common to all system administrators is that "Aha!" moment when we discover a feature, service, or applet that is relatively unknown, but seems just right.
I feel that way about managing RAID sets on a Windows 2000 machine.
RAID remains one of the fundamental strategies for providing reliability for disk services under Windows 2000 and its predecessor Windows NT. A technology that is more than 10 years old, RAID has evolved into a mature and well-understood solution for high-availability storage.
In fact, RAID itself has changed very little from its initial incarnation. There have been only two new levels -- RAID 0 and RAID 6 -- added in recent years. It seems unlikely that new RAID levels will be developed. The RAID Advisory Board seems intent on explaining RAID and its options to new system administrators.
That's just as well. New levels of RAID isn’t what we need. More important for system administrators working in enterprises with substantial storage requirements are better tools for the administration of higher-availability disk systems. That’s where an intriguing part of Windows 2000 enters the picture.
Volume management in Windows 2000 is controlled by a combination of the FTDisk driver and the far more flexible Logical Disk Manager. FTDisk manages what Windows 2000 calls basic disks: simple and extended partitions and fault-tolerant sets. The Logical Disk Manager (LDM) provides a level of abstraction on top of those basic volume management tools.
The main difference between FTDisk and LDM is that LDM creates its volumes on soft partitions. Each physical disk gets a single hard partition. LDM then creates a database that manages all the logical disk volume information. This level of abstraction provides several benefits for storage administrators, including the new Distributed File System and NT File System enhancements.
Best of all, RAID sets can now be created, broken, rebuilt, and administered online -- all from the relative comfort of the Management Console. Having a graphical tool that supports the configuration and management of multiple RAID systems from a central console is a real boon. It’s an improvement, but it’s not perfect yet. One thing that I would like to see added is more robust alarm notification.
It’s easy enough to set up Microsoft’s Management Console so an audible alarm accompanies any error relating to a RAID system. What would be nice would be timely incident notification using an array of communications strategies -- including pager, cell phone, and e-mail. The architecture of LDM is set up in such a way that I think we can expect to see third-party tools in this space.
Another example of what’s still missing in Windows 2000 is the absence of tools for automated performance monitoring of RAID systems. Windows 2000 already gives us extensive monitoring options for I/O subsystems, but the tools for monitoring RAID controllers are skimpy by comparison. When system administrators set up RAID configurations, they naturally make decisions about key parameters -- cache size, for example -- that they may want to change as the system gets used. Without good monitoring tools, managing high-reliability disk systems is largely a trial-and-error exercise.
This may become even more important as Web servers get attached to databases. As application workload characteristics change, configuration flexibility will only become more important. In fact, it would really help if the configuration tools for a high-availability I/O subsystem were aware of the I/O characteristics of the underlying databases and BackOffice tools. Such tools would give a system administrator the intelligence needed to build the best array configuration possible for a given combination of software and application I/O characteristics.
I suspect third-party tools for supporting RAID system performance monitoring, and for supporting dynamic reconfiguration of RAID systems based on real-time utilization, are around the corner. While Microsoft’s Management Console doesn’t provide these tools natively, it does support the addition of third-party tools to extend the value of the disk system.
One recent survey indicates that almost 25 percent of a data center budget is devoted to storage. With so much depending on that investment, RAID has become the cornerstone in ensuring availability for an organization’s applications. With RAID being such an essential feature of larger systems, we can expect the new flexibility of Windows 2000’s storage architecture to be exploited by third-party management and performance tools.
If those tools address RAID configuration and monitoring, I suspect we’ll think they’re just right. --Mark McFadden is a consultant and is communications director for the Commercial Internet eXchange (Washington). Contact him at email@example.com.