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did far more than a PC needed—a SCSI−I or II controller, for example, can handle up to seven disks or other
devices. Because a PC rarely has more than one or two hard drives, and other components are usually in the
form of Industry−Standard Architecture, or ISA, cards, PC designers decided that they might be able to reduce
costs by removing this flexibility. They came up with IDE disks, where the controller is actually integrated
into the disk itself, leaving only an ISA interface card on the PC’s motherboard.
As PCs became popular, IDE disks quickly became the most common commodity disks, and prices dropped
far below those of other disk types. However, the shortcuts taken in the design of IDE caused problems later,
and every time a new difficulty arose, someone added a new “standard” to the specification. For example, the
IDE interface didn’t support CD−ROM drives, so hardware
engineers squeezed ATAPI into the design. (ATAPI, or AT Attached Packet Interface, connects CD−ROM
and tape drives to the IDE interface.) In modern PCs, it isn’t even strictly true that the disks sit behind an
interface anymore—it’s hard to draw a clear line between the controller and the interface.
Like most PC motherboards, VMware Workstation has two IDE controllers, called the primary and secondary
interfaces. The virtual hardware is the Intel 82371AB PIIX4 chipset. The IRQ (or interrupt request) and port
assignments are as follows:
Interface IRQ I/O Ports
Primary 14 0x01f0 to 0x01f7, 0x03f6
Secondary 15 0x0170 to 0x0177, 0x0376
Like all IDE interfaces, each of these ports can support a maximum of two devices (sometimes called master
and slave devices). Under VMware, they are limited to disk, CD−ROM/DVD−ROM, CD−R, and CD−RW
drives that you can configure in a few different ways.
VMware stores virtual and plain disks as files on your host system. These files are images of a complete disk
and are usually quite large. A raw disk is a mapping from one of your real disks to a disk under VMware.
VMware disks provide some added flexibility that you don’t have with disks on a real machine, such as the
ability to undo or make a disk appear as read−write without actually altering the data underneath. You may
also configure VMware ATAPI CD−ROM drives as mappings to a real disk, or if you have a CD−ROM
image on your host system (such as an ISO9660 file), you can point VMware to that. (See page 58 for more
information on all of these modes and section 11.4 for a discussion of CD−ROM images.)
2.2.2 SCSI Disks
The small computer system interface, or SCSI, is a peripheral bus standard for small computers, meant for
attaching various devices to a computer. The bus is independent of the computer’s architecture, so you can,
for example, exchange SCSI devices between PC and Sun systems, assuming that you have the drivers for
those particular kinds of devices on those systems. The gateway between the SCSI bus and a computer is
called a SCSI host controller, though it’s often known as a SCSI adapter or SCSI card.
There are several types of SCSI buses: SCSI−I, SCSI−II, Fast SCSI−II, Ultra Wide SCSI, and so on. SCSI−I
and II can have up to eight devices on a bus (this number includes the host controller). Wide SCSI can handle
up to 16 devices. If you’re interested in SCSI, a good place to look is The Book of SCSI, 2nd Edition (another
No Starch Press publication; ISBN 1−886411−10−7).
VMware Workstation has virtual SCSI hardware. Its host controller is a PCI−based BusLogic BT−958 Ultra
Wide SCSI adapter. You can configure up to seven disks or CD−ROM drives from VMware’s controller,
Chapter 2: The VMware Virtual Machine
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