Monitoring Disk Sets

Two heads are better than one. In fact, when it comes to disks, the more heads the better, if you can keep them all busy. Because each physical disk typically has its own head stack assembly, and the heads work simultaneously, performance on disk sets can be significantly better on than single disks. However, some disk configurations are designed for data security, with performance as a secondary concern.

The Windows NT 4.0 Workstation Disk Administrator supports many different disk configurations, including volume sets, which are logical combinations of multiple physical disks. Performance Monitor and other monitoring tools can be set up to measure and help you tune performance on volume sets.

Note

Whenever you combine noncontiguous physical disk space into a logical partition, the Disk Administrator adds Ftdisk.sys, a fault tolerant driver, to your disk driver stack and starts the FTDISK service. To see if FTDISK is started in your computer, check the Devices Control Panel.

There are three main strategies for combining physical disks. The terms introduced here are used throughout this section:

Term	Description

RAID (Redundant Array of Inexpensive Disks)	A standard technology for combining multiple physical disks into one or more logical disks.
Hardware RAID	Separate physical disks combined into one or more logical disks by the disk controller or disk storage cabinet hardware.
Software RAID	Noncontiguous disk space combined into one or more logical partitions by the fault tolerant software disk driver, FTDISK. This includes separate physical disks or noncontiguous space on a single physical disk.
Stripe sets	Associated free space on up to 32 different physical disks. When you write to a stripe set, some of the data is written to each of the physical disks in the set. Stripe sets are a type of software RAID that use FTDISK.
Mirror sets	Associated free space of the same size on two physical disks. When you write to a mirror set, the same data is written to each of the disks. This creates a real-time backup of the data. Mirror sets are supported only on Windows NT Server.
Stripe sets with parity	Associated free space on three or more disks. When you write, the file data and the parity data are distributed across all disks. Stripe sets with parity sets are supported only on Windows NT Server.