Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Reexamination Certificate
1997-06-10
2001-02-06
Sniezek, Andrew L. (Department: 2753)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
C360S053000, C711S171000
Reexamination Certificate
active
06185058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to no-ID data storage disk drive systems and more particularly to data sector formatting operations in such systems.
2. Description of the Prior Art
In data storage systems such as magnetic disk drives, digital information is magnetically stored upon a surface of a magnetic medium such as a magnetic storage disk in a set of concentric circular patterns called tracks. The digital information is represented by selectively polarizing the surface of the disk. When this information is read back from the disk, the magnetic polarization of the medium is sensed and converted to an electrical output signal. The read and write operations are performed by read/write electronics in conjunction with a read/write head which flies over the surface of the rotating disk and provides an output signal.
Typically, storage disks of a disk drive are stacked in a disk stack which are mounted for rotation together on a single spindle. Each side of each disk in the disk stack has a surface which is usually used to store information. Each surface of a disk in the disk stack is usually exposed to at least one head responsible for reading and writing information on that particular surface. Typically, all the magnetic heads are mounted on actuator arms and move in tandem over the surfaces of the disk so that they are all at the same approximate disk radius at the same time.
In order to accurately move a magnetic head to a desired track and position the head over that track a servo system is utilized. The servo system performs two distinct functions known as the “seek” or “access” function and the “track following” function. During the seek operation the servo system moves a read/write head to a selected track from a previous track or from a parked position as quickly as possible. When the head reaches the desired track, the servo system begins a track following operation in which it accurately positions the head over the center line of the selected track and maintains the head in that position as successive portions of the track pass by the head.
During a seek operation the actuator arm where the head is located is moved as fast as possible so as to minimize the time required for that operation. Since the seek time is one of the most important factors considered in measuring the overall performance of disk drives, it is essential to minimize the time it takes for carrying out the seek operation.
In order to read and write data from the correct location in the disk stack, the data sectors in the disk stack are identified by cylinder address, head address and sector address (CHS). A cylinder identifies a set of specific tracks on the disk surfaces in the disk stack which lie at equal radii and are, in general, simultaneously accessible by the collection of heads. The head address identifies which head can read the data and therefore identifies the disk surface on which the data is located. Each track within a cylinder is further divided into sectors for storing data and servo information.
Many modern disk drives use a concept known as zone bit recording (ZBR) as taught by Hetzler in U.S. Pat. No. 5,210,660, and assigned to the assignee of the present invention, in which the disk surface is divided into radial zones and the data is recorded at a different data rate in each zone. The addition of zones requires expansion of the cylinder, head, sector (CHS) identification scheme to a zone, cylinder, head, sector (ZCHS) identification scheme.
Some disk drives have servo information only on a dedicated surface on one disk in the disk stack. However, many modern disk drives use a servo architecture known as sectored servo (also referred to as sector servo) as taught by Hetzler in U.S. Pat. No. 5,210,660 where servo information is interspersed with the data stored on each disk surface. The servo sector in sectored servo architecture contains position data on each track to help the magnetic head stay on that track. This approach is preferred because it can be implemented at low cost without extra components beyond those required for storing data and because it provides the servo information at the data surface which is being accessed, thereby eliminating all thermal sources of track misregistration (TMR).
The use of either sectored servo or dedicated servo surface architectures and the implementation of either of the two are well known to those skilled in the art.
There are also a number of methods used to format disk files, one of which is fixed block architecture (FBA) method which is used in both dedicated servo disk files and sectored servo disk files. In an FBA formatted disk file, each disk track is divided into a number of equal sized segments, and each segment is divided into sectors containing servo information, identification information (ID), and data.
FIG. 1
shows a typical segment
9
of a track on a FBA formatted disk utilizing sectored servo architecture. Segment
9
comprises sequentially a servo sector
10
, an identification (ID) region
11
and a data sector
12
. Servo sector
10
further comprises information such as write/read and speed field
15
, address mark (AM) field
16
and position error signal (PES) field
17
. The ID region
11
, which is written onto the disk during the format operation contains specific information concerning the data sector
12
which can be used during normal operation, either writing or reading, to identify the succeeding data sector
12
. The ID region
11
typically comprises a read/write and speed field
18
, VCO sync field
19
encoder/decoder flush field
20
, sync byte
21
, and ID and CRC field
22
. The data sector
12
typically comprises fields
23
-
26
which correspond to the ID fields
18
-
21
and data and ECC field
27
. In a disk file having an ID region, the CHS/ZCHS information (otherwise known as logical block address (LBA)) is typically recorded on the data ID field
22
immediately proceeding the data sector.
Recently, a new method and system has been developed to increase capacity of disk drives known as the no-ID format and the disk drive systems utilizing no-ID format are commonly referred to as no-ID disk drive systems. This format has been taught by Best et al in U.S. Pat. No. 5,438,559 and assigned to the assignee of the present invention. For no-ID disk drives implementing a sector servo architecture, a full track number identifier in the position field in the servo sector of a given track is used in combination with a defect map to uniquely identify the requested data sectors and thereby completely eliminate the use of ID regions.
Once a disk drive completes the required seek operation to the cylinder and head identified, or to the zone, cylinder and head identified, the recording channel scans the desired data sector by examining the servo sector associated with each data sector as it passes under the head. When the appropriate data sector is found, the data is read and the operation is completed.
One problem encountered with disk drive systems (both ID and no-ID) has been that the data sector format operation is time consuming, expensive, and does not allow for ease of reformatting. The complete disk format operation consists of writing the servo sectors, data sectors and ID sectors (in the case of ID drives) along the concentric tracks of the magnetic recording disk. Typically, the entire operation is performed by the manufacturer, however, the customer may also do a data sector format operation.
The complete disk formatting process at the time of manufacture starts with a blank magnetic disk in a disk drive system. The servo sectors are then written using specialized machinery known as servo writers. The servo writers help to exactly position the magnetic head while it is writing the servo sectors. It is very important that the servo sectors be accurately positioned since they are used to position the head along the track during operation of the disk drive. The servo sectors are typically written at some specified angular distance from one ano
Dobbek Jeffrey Joseph
Lam Laura Sheung-ching
Altera Law Group LLC
International Business Machines - Corporation
Neal Regina Y.
Sniezek Andrew L.
LandOfFree
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