Abstract: A solid state drive (SSD) includes an SSD control module configured to determine frequencies corresponding to how often data stored in respective logical addresses associated with the SSD is updated and form groups of the logical addresses according to the frequencies, and a memory control module configured to rewrite the data to physical addresses in blocks of an SSD storage region based on the groups.

Abstract: A system including first and second memory and a control module. The first memory stores a first lookup table with first metadata that includes a first mapping between logical and physical addresses and is lost due to an unexpected power down event. The second memory stores a second lookup table with second metadata and an event log. The second metadata includes a second mapping between the logical and physical addresses. The event log includes entries indicating updated associations between respective ones of the logical addresses and one of the physical addresses as included in the first metadata prior to the power down event. The control module: prior to the power down event, performs segmented flushes each including updating a segment of the second metadata with a corresponding segment of the first metadata; and walks the event log to recover a full flush cycle of segments of the first metadata.

Abstract: A memory includes first memory configured to store first data indicating relationships between logical addresses and respective physical addresses, wherein the physical addresses are arranged in a plurality of different groups, respective statuses of each of the plurality of different groups, and an activity log indicating when any of the respective statuses has changed. A second memory is configured to store second data in memory locations corresponding to the physical addresses and, in response to a respective status of one of the plurality of groups changing, store a portion of the first data corresponding to the one of the plurality of groups. A recovery module is configured to update, in response to the activity log indicating that the respective status of the one of the plurality of groups has changed, the first data with the portion of the first data corresponding to the one of the plurality of groups.

Abstract: Systems and techniques relating to servo systems include, according to an aspect, a method includes: causing writing of a band of spirals including a first spiral set and a second spiral set onto a storage medium; determining one or more characteristics associated with the band of spirals; identifying one or more spirals of the band of spirals that meet the one or more determined characteristics; and determining an end of the band of spirals based on the one or more identified spirals. The method can further include causing writing of servo information onto the storage medium while track following on the band of spirals; causing terminating of the writing of the servo information upon determining the end of the band of spirals; and causing writing of another band of spirals starting at the end of the previous band of spirals.

Abstract: A system including first and second memories and a control module. The first memory stores a first lookup table (LUT) with first metadata. The first metadata maps logical addresses to physical addresses. The first metadata is lost due to an unexpected power down event. The second memory stores an event log and a second LUT with second metadata. The second metadata maps the logical addresses to the physical addresses. The event log includes entries that indicate updated associations between the logical addresses and the physical addresses. The control module, prior to the unexpected power down event, performs segmented flushes that include updating segments of the second metadata with segments of the first metadata.

Abstract: A system includes a first memory configured to store a first lookup table (LUT) with first metadata. A second memory is configured to store a second LUT with second metadata, wherein the first metadata includes a first mapping between logical addresses and physical addresses. The second metadata includes a second mapping between the logical addresses and the physical addresses. A control module is configured to update the first metadata. The control module is configured to update segments of the second metadata based on the first metadata at respective predetermined times. Each of the segments refers to a predetermined number of entries of the second LUT.

Abstract: Methods, systems and computer program products for detecting an end of a reference spiral band are described. A first portion of servo information may be written on a disk using the reference spiral band. By detecting an end of a reference spiral band, a new reference spiral band may be launched. A read/write head of a hard disk drive may subsequently use the new spiral band to write the remaining portion of the servo information, which aids the writing of data tracks on the disk.

Abstract: The present disclosure includes systems and techniques relating to self-servo-writing. In some implementations, a method includes determining a spiral velocity associated with writing a plurality of reference spiral sets; identifying a plurality of launching tracks based on a predetermined ratio and the spiral velocity, where each of the plurality of launching tracks is associated with one of the plurality of reference spiral sets; writing each of the plurality of reference spiral sets starting at its associated launching track; and writing one or more sets of servo wedges using the plurality of reference spiral sets, where the reference spiral sets and the one or more sets of servo wedges are written at the predetermined ratio.

Abstract: Methods, systems, and apparatus, including computer program products, are described for calibrating servos, and in some implementations for calibrating spiral servos for use in self servo write processes. In one aspect, a method is provided that includes measuring a slope of a spiral written to a machine readable medium, and adjusting a parameter in accordance with the measured slope to calibrate spacing of servo tracks, with respect to variation between a target slope and the measured slope for the spiral, for writing the servo tracks to the machine readable medium using the spiral as a reference and the adjusted parameter to generate a same radial spacing between servo tracks from spirals with different slopes.

Abstract: A memory includes first memory configured to store first data indicating relationships between logical addresses and respective physical addresses, wherein the physical addresses are arranged in a plurality of different groups, respective statuses of each of the plurality of different groups, and an activity log indicating when any of the respective statuses has changed. A second memory is configured to store second data in memory locations corresponding to the physical addresses and, in response to a respective status of one of the plurality of groups changing, store a portion of the first data corresponding to the one of the plurality of groups. A recovery module is configured to update, in response to the activity log indicating that the respective status of the one of the plurality of groups has changed, the first data with the portion of the first data corresponding to the one of the plurality of groups.

Abstract: A system includes first memory configured to store first metadata to associate logical addresses with physical addresses. Second memory is configured to include the physical addresses, to store first data based on the physical addresses, and to store portions of the first metadata when a status of a predetermined group of the physical addresses is changed. A recovery module is configured to update the first metadata based on the portions of the first metadata stored in the second memory.

Abstract: Methods, systems, and apparatus, including computer program products, are described for calibrating voice coil motors. In one aspect, a method is provided that includes seeking toward an outer diameter of a machine readable medium from a target servo track to a blank portion of the machine readable medium. A radial velocity of an actuator is determined after accelerating the actuator to a target radial velocity. The radial velocity is compared to the target radial velocity, and a current, that is used to controllably modify the radial velocity of the actuator if the radial velocity is different from the target radial velocity, is calibrated.

Abstract: Methods, devices and systems include, in some implementations, a method including: writing, using a head having a read element and a write element, a band of spiral sets, the band of spiral sets including a first spiral set and a second spiral set different from the first spiral set; writing, using the write element, servo information that includes one or more sets of servo wedges while the read element is servoing on the first spiral set; and servoing the read element on the second spiral set based on one or more determined conditions under which writing the servo information coincides with reading data from the first spiral set.

Abstract: A solid state drive (SSD) includes an SSD control module configured to determine frequencies corresponding to how often data stored in respective logical addresses associated with the SSD is updated and form groups of the logical addresses according to the frequencies, and a memory control module configured to rewrite the data to physical addresses in blocks of an SSD storage region based on the groups.

Abstract: Methods, systems and computer program products for detecting an end of a reference spiral band are described. In some implementations, a band of spirals and servo information are written onto a storage medium. One or more characteristics associated with the band of spirals are determined. Then, one or more spirals of the band of spirals are identified as reference spirals based on the one or more determined characteristics. The writing of at least one of the band of spirals and the servo information is terminated upon identifying the one or more reference spirals.

Abstract: Systems, methods, and apparatuses, including computer program products, are described for, in at least one implementation, determining a measured slope of a spiral, calibrating radial spacing between servo tracks according to a relationship between a target slope and the measured slope, wherein an amount of calibration for the radial spacing varies directly with the relationship between the target slope and the measured slope, and generating servo tracks according to the calibrated radial spacing.

Abstract: Methods, systems and computer program products for launching one or more reference spiral sets using different tracks are described. In some implementations, a method can be used that includes writing a first spiral set starting at a first track and determining a radial offset. Then a second track is determined based on the radial offset. A second spiral set is also written starting at the second track. A spiral set-to-wedge ratio is determined based on a number of spiral sets to be written. Subsequently, servo information can be written using the first spiral set and the second spiral set. The servo information can include one or more sets of servo wedges, which can be written based on the spiral set-to-wedge ratio.

Abstract: A system includes a first memory configured to store a first lookup table (LUT) with first metadata. A second memory is configured to store a second LUT with second metadata, wherein the first metadata includes a first mapping between logical addresses and physical addresses. The second metadata includes a second mapping between the logical addresses and the physical addresses. A control module is configured to update the first metadata. The control module is configured to update segments of the second metadata based on the first metadata at respective predetermined times. Each of the segments refers to a predetermined number of entries of the second LUT.

Abstract: Methods, systems, and apparatus, including computer program products, are described for calibrating voice coil motors. In one aspect, a method is provided that includes seeking toward an outer diameter of a machine readable medium from a target servo track to a blank portion of the machine readable medium. A radial velocity of an actuator is determined after accelerating the actuator to a target radial velocity. The radial velocity is compared to the target radial velocity, and a current, that is used to controllably modify the radial velocity of the actuator if the radial velocity is different from the target radial velocity, is calibrated.

Abstract: A method for dynamic spiral ISR scheduling determines a dynamic delay with spiral to spiral spacing information of a disk, so as to ensure that the sum of a primary ISR time and a secondary ISR time does not exceed the wedge to wedge time. The ISR time may be scheduled to start after a delay for the sum of a static delay and the dynamic delay from an edge. A system for dynamic spiral ISR scheduling uses a dynamic delay determining unit to determine a dynamic delay, and an ISR scheduling unit to schedule the start of a secondary spiral set ISR based on a sum of the dynamic delay and a static delay.