Disk resident split data sector information management system on a headerless magnetic disk device

#This invention relates to the field of magnetic disk device formats, and in particular to a disk resident system for managing split data sector information in a split data sector information field of headerless format magnetic disk device.

#A specific point on the concentric tracks of a magnetic disk is identified by a unique address that typically includes a cylinder number, a head number, and data sector number. To help position a read/write head over a specific point on the magnetic disk, special markers called servo bursts are located at regularly spaced intervals throughout the recording surface of the magnetic disk. The servo bursts each contain a cylinder, head, and servo burst number that are used to orient the read/write heads so that a target address on the magnetic disk can be located. The cylinder and head portion of a target address identify a specific track on the magnetic disk and the data sector portion of a target address identifies a specific data sector on the track. Because there are a fixed number of bytes in a data sector and there are a fixed number of bytes between servo bursts on a given track, the exact location of a target data sector can be calculated once the track is located.

#One problem with calculating the exact location of a target data sector that is located between two neighboring servo bursts is that the fixed length data sectors do not always fit evenly between the boundaries of two neighboring servo bursts. The result is a data sector that is split across a servo burst so that there are some number of bytes of the split data sector located on a first side of the servo burst and the remaining number of bytes are located on a second side of the servo burst. Thus, to calculate the precise location of a target data sector boundary it is necessary to know if a split data sector exists at a given servo burst boundary, and if so how many bytes of the split data sector exist following the servo burst boundary but before the first full data sector following the servo burst boundary.

#FIG. 1 illustrates a system level view of a magnetic disk device component architecture in block diagram form;

#FIG. 2 illustrates an top view of a track and sector format on a magnetic disk device recording surface;

#FIGS. 3-4 illustrate detailed views of a track and sector format in block diagram form; and

#FIG. 1 illustrates a system level architecture view of a magnetic disk device 100 in block diagram form. The primary components in magnetic disk device 100 include, but are not limited to, disk control components 110-140 and operational disk components 150-160. Disk control components 110-140 include, but are not limited to, a microprocessor or Digital Signal Processor (DSP) 110, a hard disk controller 120 with accompanying RAM 121, a servo controller 130, and a read/write channel controller 140. The microprocessor or DSP 110 is the highest level of control and coordination for all disk device activities and read/write operations executed by the disk control components. Hard disk controller 120 manages and caches all data being written to and/or read from the magnetic disk 170. RAM 121 is used as a data cache in addition to table storage for disk related information such as split data sector information and/or defective data sector information as is done in conventional magnetic disk devices. The servo controller 130 interprets servo burst information and controls positioning activities of read/write heads. Read/write channel 140 passes data to and from the various disk control components 110-130 for each read/write operation.

#Operational disk components 150-160 include, but are not limited to, a Head and Disk Assembly (HDA) 150 that includes magnetic disk 170 and read/write heads 164-167, and Voice Coil Motor (VCM)/spin controller 160 that is operatively connected to access arms 161-163. Magnetic disk 170 is comprised of one or more platters 171-172. Each platter has at least one and typically two magnetic recording surfaces as illustrated for the first and second surfaces 173-174 and 175-176 of platters 171-172 respectively. Each of the platters 171-172 of a multiple platter magnetic disk 170 are rigidly fixed to a spindle 177 along a common central axis. VCM/spin controller 160 manages the appropriate physical movements of the access arms 161-163. Read/write heads 164-167 are positioned to fly just off the recording surfaces 173-176 respectively when the magnetic disk 170 is spinning. Although other magnetic disk device architectures are possible other than the architecture described above, no limitation is intended or implied with respect to the present invention. The present invention is applicable to any headerless format magnetic or optical disk regardless of a single platter or multiple platter implementation or a removable medium or floppy disk medium.

#FIG. 2 illustrates the track and sector format for a recording surface such as recording surface 173 of magnetic disk 170. Recording surface 173 comprises a plurality of concentric tracks of successively increasing size from the center spindle 177 to the outer edge 210. The present illustration focuses on tracks 220, 230, and 240. A cylinder is the set of all tracks of a given size from each recording surface of each platter in magnetic disk 170. Thus, if track 230 is the 6th concentric track of recording surface 173 and each recording surface of magnetic disk 170 has a 6th concentric track, then there exists a 6th cylinder for magnetic disk 170 that comprises each 6th concentric track of each recording surface. With a single motion of access arms 161-163, each read/write head 164-167 can be simultaneously positioned to read and/or write data from any one or more of the recording surfaces 173-176 in cylinder 6. If track 230 is the 6th track and read/write heads 164-167 are numbered 00 through 03 respectively, then the cylinder CC and head HH address for track 230 on recording surface 173 would be "0600".