Abstract: A technique for recovering of “squeezed” sectors in a set of sequential sectors such as are used in Shingled Magnetic Recording (SMR) is described. Embodiments of the invention use a programmable erased sector recovery scheme, which is a concatenation of a “Cauchy-type” track erasure correction code, together with a media-error correction code that generates N-weighted parity-sectors per track and is capable of replacing up to N-erased sectors per track in any possible combination.

Abstract: Disk drives are described in which blocks of data spanning multiple sectors are encoded into a plurality of codewords which are then divided into segments that are physically separated (distributed) on the disk surface over multiple sectors in a distributed codeword block so that the codewords have an improved worst case SNR in comparison to individual sectors. This results in more even SNR performance for each codeword, which improves the performance for portions of a track which have lower than the average SNR. Embodiments are described in which the distributed codeword blocks span across tracks.

Abstract: Disk drives are described that include a hybrid servo patterns in which the augmented servo burst fields, which can be Integrated Servo sequences, that provide the PES and also supply additional information such as a SAM, LSBs of the track identifier (TID), sector number, depending on the specific embodiment. Embodiments without write-to-read gaps before the servo sector SIDs are described. The augmented servo burst fields can be read after gapless writing of the preceding data area. For seeking operations the needed bits of the TID without having to detect or decode the Integrated Servo sequences or other augmented servo burst fields. Depending on the embodiment all or the most significant bits of the track identifier can be obtained during seeks by reading the TID fields passing under a read head as the read head moves across tracks without having to detect or decode the Integrated Servo sequences.

Abstract: Disk drives are described that include a hybrid servo patterns in which the augmented servo burst fields, which can be Integrated Servo sequences, that provide the PES and also supply additional information such as a SAM, LSBs of the track identifier (TID), sector number, depending on the specific embodiment. Embodiments without write-to-read gaps before the servo sector SIDs are described. The augmented servo burst fields can be read after gapless writing of the preceding data area. For seeking operations the needed bits of the TID without having to detect or decode the Integrated Servo sequences or other augmented servo burst fields. Depending on the embodiment all or the most significant bits of the track identifier can be obtained during seeks by reading the TID fields passing under a read head as the read head moves across tracks without having to detect or decode the Integrated Servo sequences.

Abstract: A technique for recovering of “squeezed” sectors in a set of sequential sectors such as are used in Shingled Magnetic Recording (SMR) is described. Embodiments of the invention use a programmable erased sector recovery scheme, which is a concatenation of a “Cauchy-type” track erasure correction code, together with a media-error correction code that generates N-weighted parity-sectors per track and is capable of replacing up to N-erased sectors per track in any possible combination.

Abstract: A “write-squeeze-verify” method is used for verification of the data that has been written in the annular bands of a shingled magnetic recording disk drive. The writing of data along a track overwrites a portion of the previously written track and thus “squeezes” the data of the previously written track to thereby form a “shingled data track” (SDT). The data in each SDT is read back and verified by an error correction check using error correction bits associated with the data written in the SDT, or by comparing the readback data with the data stored in memory. If the data read back is not verified, a write error counter is incremented and a write error frequency is calculated. One or more attempts to write the data can be performed. If the data in the SDT cannot be verified after the attempted rewrite(s), then a “re-try fail” is reported.

Abstract: A method and a storage system are provided for implementing fragmented stream handling for persistent media including shingled disk drives (SDDs). A plurality of Exception Regions for recording stream commands is defined for disk regions. One state is maintained in each of the Exception Regions including a free Exception Region, an active Exception Region, a recovery Exception Region and a used Exception Region. TRIM commands are issued by a host to the drive to indicate deleted content.

Abstract: An indirection system in a shingled storage device is described that uses an algorithm to map LBAs to DBAs based on a predetermined rule or assumption and then handles as exceptions LBAs that are not mapped according to the rule. The assumed rule is that a fixed-length set of sequential host LBAs are located at the start of an I-track. Embodiments of the invention use two tables to provide the mapping of LBAs to DBAs. The mapping assumed by the rule is embodied in the LBA Block Address Table (LBAT) which gives the corresponding I-track address for each LBA Block. The LBA exceptions are recorded using an Exception Pointer Table (EPT), which gives the pointer to the corresponding variable length Exception List for each LBA Block. The indexing into the LBAT and the EPT is derived from the LBA by a simple arithmetic operation.

Abstract: Shingled magnetic recording (SMR) devices are described that include a command processor for accepting commands from the host/user for executing selected SMR related operations, setting selected SMR parameters and reading selected SMR related statistics and status indicators. The commands allow a host/user to control defragmentation and destaging operations. Embodiments include some or all of the set of features allowing selection of formatting settings, selection of optimization settings; command to immediately run defragmentation operation; command to change waiting time before starting defragmentation operation; and command to temporarily suspend defragmentation operation until certain usage threshold is met (e.g., E-region(s) near full).

Abstract: Pre-patterned discrete track media for self-servo writing are described. Embodiments include land and groove patterns for two or more Integrated Servo sequence fields for each servo sector in which one of the Integrated Servo sequence fields is aligned with the data track and a second sequence is offset by one-half of a track width. The lands and grooves between the Integrated Servo sequence fields are preferably the same width as those between the data tracks to facilitate planarization. Alternative embodiments include a sync feature for each servo sector formed by a selected groove and/or land pattern as a marker for the start of the servo fields. Alternative embodiments include a bootstrap zone with servo patterns that are readable when DC-magnetized. Described methods of self-servowriting include ways to adapt to eccentricity and non-circularity of pre-patterned discrete tracks with respect to the head paths.

Abstract: A “write-squeeze-verify” method is used for verification of the data that has been written in the annular bands of a shingled magnetic recording disk drive. The writing of data along a track overwrites a portion of the previously written track and thus “squeezes” the data of the previously written track to thereby form a “shingled data track” (SDT). The data in each SDT is read back and verified by performing an error correction check using error correction bits associated with the data written in the SDT, or by comparing the readback data with the data stored in memory. If the data read back is not verified, a write error counter is incremented and a write error frequency is calculated. One or more attempts to write the data can be performed. If the data in the SDT cannot be verified after the attempted rewrite(s), then a “re-try fail” is reported.

Abstract: A method and a storage system are provided for implementing fragmented stream handling for persistent media including shingled disk drives (SDDs). A plurality of Exception Regions for recording stream commands is defined for disk regions. One state is maintained in each of the Exception Regions including a free Exception Region, an active Exception Region, a recovery Exception Region and a used Exception Region. TRIM commands are issued by a host to the drive to indicate deleted content.

Abstract: An embodiment of the present invention implements some or all major servo subfunctions for a storage device in integrated servo fields comprising sequences of encoded bits having selected mathematical properties. The integrated servo field is composed of a number of encoded sequences, which are members of a selected sequence set that is constrained to preferably provide some or all of the following functions: the Servo Track Mark (STM), the Position Error Signal (PES) and positional information such as the track-ID. In one embodiment the plurality sequences encoding a location identifier such as a track-ID are distributed across a set of servo wedges. A method of encoding the location identifier using a Chinese Remainder Theorem is described.

Abstract: Shingled magnetic recording (SMR) devices are described that include a command processor for accepting commands from the host/user for executing selected SMR related operations, setting selected SMR parameters and reading selected SMR related statistics and status indicators. The commands allow a host/user to control defragmentation and destaging operations. Embodiments include some or all of the set of features allowing selection of formatting settings, selection of optimization settings; command to immediately run defragmentation operation; command to change waiting time before starting defragmentation operation; and command to temporarily suspend defragmentation operation until certain usage threshold is met (e.g., E-region(s) near full).

Abstract: Shingled magnetic recording (SMR) devices according to embodiments of the invention include unshingled cache regions that can be used for storage of data. The unshingled cache regions can be used in a variety of flexible ways including in an implementation of write-twice caching or for opportunistic temporary storage to improve performance. The cache regions can be offset between top and bottom surfaces of the disk and staggered between disks to provide shorter seek times to the nearest cache region. Embodiments of the invention are adapted for use with symmetric or asymmetric heads.

Abstract: Methods are described that allow disk drives, such as shingle-written magnetic recording (SMR) drives, to recover an Indirection Address Table mapping of LBAs to PBAs after an emergency power off (EPO). Indirection Address Table (IAT) snapshots are periodically written inline with user data stores, and in one embodiment Cumulative Delta Lists (CDLs) with incremental address update information are stored between snapshots. In an embodiment of the invention, when an imminent loss of power is detected, the current CDL, covering IAT updates not yet written to disk, is saved to a nonvolatile memory. The IAT snapshots combined with the set of CDLs provide the information needed to recreate the current Indirection Address Table when power is restored after an emergency power loss. In an alternative embodiment the CDL is obviated by including metadata in the sector that encodes the address indirection mapping and the last snapshot ID.

Abstract: An indirection system in a shingled storage device is described that uses an efficient algorithm to map LBAs to DBAs based on a predetermined rule or assumption and then handles as exceptions LBAs that are not mapped according to the rule. The assumed rule is that a fixed-length set of sequential host LBAs are located at the start of an I-track. Embodiments of the invention use two tables to provide the mapping of LBAs to DBAs. The mapping assumed by the rule is embodied in the LBA Block Address Table (LBAT) which gives the corresponding I-track address for each LBA Block. The LBA exceptions are recorded using an Exception Pointer Table (EPT), which gives the pointer to the corresponding variable length Exception List for each LBA Block. The indexing into the LBAT and the EPT is made efficient by deriving the index from the LBA by a simple arithmetic operation.

Abstract: Pre-patterned discrete track media for self-servo writing are described. Embodiments include land and groove patterns for two or more Integrated Servo sequence fields for each servo sector in which one of the Integrated Servo sequence fields is aligned with the data track and a second sequence is offset by one-half of a track width. The lands and grooves between the Integrated Servo sequence fields are preferably the same width as those between the data tracks to facilitate planarization. Alternative embodiments include a sync feature for each servo sector formed by a selected groove and/or land pattern as a marker for the start of the servo fields. Alternative embodiments include a bootstrap zone with servo patterns that are readable when DC-magnetized. Described methods of self-servowriting include ways to adapt to eccentricity and non-circularity of pre-patterned discrete tracks with respect to the head paths.

Abstract: A patterned-media perpendicular magnetic recording disk has patterned servo regions and is nanoimprinted from a master mold made using directed self-assembly of block copolymers. The disk has patterned concentric circular data tracks of discrete data islands, with the tracks having a track pitch in the radial or cross-track direction. The disk also has patterned servo sectors extending generally radially across the patterned data tracks. The servo pattern is a chevron pattern of slanted or non-radial stripes that have a stripe pitch in the cross-stripe direction substantially equal to the track pitch. As a result of the method of making the master mold, the nanoimprinted disk has a chevron servo pattern with non-radial stripes that are magnetized segments of radial lines separated by nonmagnetic spaces.

Abstract: A magnetic recording disk drive has a position-error-signal (PES) servo pattern divided into at least two circumferentially adjacent fields that extend radially across the data tracks and include PES blocks that are DC magnetized in one direction, with each PES block having a magnetization opposite to the magnetization of its radially adjacent neighboring PES blocks. Each PES field is contiguous with and shifted radially relative to its circumferentially adjacent neighbor PES fields. Each PES block has a single DC magnetization, and the length of the magnetization is substantially longer than the length of the magnetizations in the other fields of the servo pattern.