CIS 170F: Windows 7 Administration

Week 4

Managing Disks
Disk Technology
Multiple Disks as One Logical Disk

  • A logical disk appears to the Windows 7 operating system as if it is one disk drive. Single internal, external, and VHD disks can all be examples of logical drives.

  • There are two reasons for grouping multiple physical drives together to appear as one logical drive:
    1. Creating a logical drive that has more combined space than one physical drive alonecan have.
    2. Adding fault tolerance that allows for a physical drive to fail without losing access to the logical drive.

  • Windows 7 can combine multiple disks as one logical disk using software built into the operating system. The combination of disks and how they store data is defined by RAID standards. RAID is an acronym for Redundant Array of Inexpensive Disks. This is a collection of disk management strategies to either combine data space from multiple disk drives to look like one bigger drive or provide fault-tolerance so individual disks can fail without losing data. Some advanced RAID strategies provide fault-tolerance and disk space aggregation at the same time. RAID technology implements complex operations to manage the data disks involved. Either the operating system or a dedicated hardware controller can run the code necessary to manage different types of RAID.

    Windows 7 can implement RAID (Redundant Array of Inexpensive Disks) operations through software but the performance may be limited by how busy the processor is while it is also running applications. Instead of using operating system software to combine space from multiple drives, multiple disks can be connected to an advanced hardware based RAID disk controller. Not all computers have an advanced hardware-based RAID disk controller or have the option of adding one. They are more often found in high-end business-class desktop computers. The use of an advanced hardware-based disk controller in a computer is possible only if Windows 7 has a supported device driver installed that def nes how the operating system can interact with that disk controller and the disks attached to it.

  • Multiple disks can be connected to an advanced hardware based RAID disk controller. The physical drives are managed by the disk hardware controller directly and management operations are done with the management software that comes with the third-party hardware. The disk hardware controller can implement hardware-based RAID arrangements without Win- dows 7 knowing it is doing so. From the perspective of the operating system, Windows 7 would see the combined multiple disks as one logical drive.

    The advantage of an advanced hardware-based disk controller implementing RAID is that it may be faster than having Windows 7 implement the same RAID-based logical drive through software. Hardware based disk controllers can also implement RAID modes that Windows 7 cannot implement in software, such as RAID 5. The disadvantages include increased hardware cost, compatibility issues with operating system device drivers, and having to learn a third-party management tool to configure and maintain the attached disks.