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Appendix A
BREAKING THE 137 GIGABYTE STORAGE
BARRIER
This appendix provides information about the 137GB storage barrier. It
discusses the history, cause and the solution to overcome this barrier.
A.1 Breaking the 137 Gigabyte Storage Barrier
Capacity barriers have been a fact of the personal computer world since
its beginnings in the early 1980’s. At least 10 different capacity barriers
have occurred in the storage industry over the last 15 years. The most
notable barriers seen previously have been at 528 megabytes and then at
8.4 gigabytes.
The ANSI NCITS T13 Technical Committee (also known as the ANSI ATA
committee) has broken this barrier by incorporating a proposal from
Maxtor into the ATA/ATAPI-6 draft standard that defines a method for
48-bit addressing on a single drive, giving more than 144 petabytes
(144,000 gigabytes) of storage.
In addition, the proposal from Maxtor that was incorporated into ATA/
ATAPI-6 defines a method for extending the maximum amount of data
that can be transferred per command for ATA devices from 256 sectors
(about 131 kilobytes) to 65,536 sectors (about 33 megabytes). This new
method is particularly useful for applications that use extremely large
files, such as those for A/V or multimedia.
The following sections will describe issues surrounding the 137-gigabyte
barrier and the solution for breaking it.
A.1.1 History
Many of the “barriers” in the past resulted from BIOS and operating
system issues caused by failure to anticipate the remarkable increases in
device storage capacity by the people who designed hard disk structures,
access routines, and operating systems many years ago. They thought,
“Who will ever have xxx much storage?” In some cases, the barriers were
caused by hardware or software bugs not found until hard disks had
grown in size beyond a certain point where the bugs would occur.
Past barriers often frustrated people trying to add a new hard disk to an
older system when they discovered that not all of the designed capacity