Abstract: The present disclosure includes systems and techniques relating to control of recording devices, such as disk drives. Systems and techniques can include controlling a motor to actuate a head about a surface of a rotating recording medium, switching from a first mode to a second mode to control the motor based on a condition of operation with respect to the rotating recording medium, and synchronizing the switch from the first mode to the second mode based on a state of electric current associated with the motor.

Abstract: A data management system or “DMS” provides a wide range of data services to data sources associated with a set of application host servers. The data management system typically comprises one or more regions, with each region having one or more clusters. A given cluster has one or more nodes that share storage. To facilitate the data service, a host driver embedded in an application server connects an application and its data to a cluster. The host driver provides a method and apparatus for capturing real-time data transactions in the form of an event journal that is provided to the data management system. The driver functions to translate traditional file/database/block I/O into a continuous, application-aware, output data stream. Using the streams generated in this manner, the DMS offers a wide range of data services that include, by way of example only: data protection (and recovery), disaster recovery (data distribution and data replication), data copy, and data query and access.

Abstract: An efficient method to apply an erasure encoding and decoding scheme across dispersed data stores that receive constant updates. A data store is a persistent memory for storing a data block. Such data stores include, without limitation, a group of disks, a group of disk arrays, or the like. An encoding process applies a sequencing method to assign a sequence number to each data and checksum block as they are modified and updated onto their data stores. The method preferably uses the sequence number to identify data set consistency. The sequencing method allows for self-healing of each individual data store, and it maintains data consistency and correctness within a data block and among a group of data blocks. The inventive technique can be applied on many forms of distributed persistent data stores to provide failure resiliency and to maintain data consistency and correctness.

Abstract: A data management system or “DMS” provides a wide range of data services to data sources associated with a set of application host servers. The data management system typically comprises one or more regions, with each region having one or more clusters. A given cluster has one or more nodes that share storage. To facilitate the data service, a host driver embedded in an application server connects an application and its data to a cluster. The host driver provides a method and apparatus for capturing real-time data modifications and application state notifications and, in response, generating data transactions in the form of an event journal that is provided to the data management system. The driver functions to translate traditional file/database/block I/O into a continuous, application-aware, output data stream.

Abstract: The present invention provides a distributed clustering method to allow multiple active instances of consistency management processes that apply the same encoding scheme to be cooperative and function collectively. The techniques described herein facilitate an efficient method to apply an erasure encoding and decoding scheme across dispersed data stores that receive constant updates. The technique can be applied on many forms of distributed persistent data stores to provide failure resiliency and to maintain data consistency and correctness.

Abstract: Systems, methods, and apparatuses including computer program products for oscillator calibration include, in at least one implementation, a storage device including: a system including a first clock source, a second clock source, and a motor controller, the motor controller including calibration circuitry configured to calibrate the second clock source according to the first clock source in response to the first clock source operating as expected, and configured to provide to the system the calibrated second clock source as a timing reference instead of the first clock source as the timing reference in response to the first clock source not operating as expected, a head actuator configured to communicate with the motor controller, and a spindle disposed within the system.

Abstract: A data management system that protects data into a continuous object store includes a management interface having a time control. The time control allows an administrator to specify a “past” time, such as a single point or range. When the time control is set to a single point, a hierarchical display of data appears on a display exactly as the data existed in the system at that moment in the past. The time control enables the management interface to operate within a history mode in which the display provides a visual representation of a “virtual” point in time in the past during which the data management system has been operative to provide the data protection service.

Abstract: A “forward” delta data management technique uses a “sparse” index associated with a delta file to achieve both delta management efficiency and to eliminate read latency while accessing history data. The invention may be implemented advantageously in a data management system that provides real-time data services to data sources associated with a set of application host servers. A host driver embedded in an application server connects an application and its data to a cluster. The host driver captures real-time data transactions, preferably in the form of an event journal that is provided to the data management system. In particular, the driver functions to translate traditional file/database/block I/O into a continuous, application-aware, output data stream. A given application-aware data stream is processed through a multi-stage data reduction process to produce a compact data representation from which an “any point-in-time” reconstruction of the original data can be made.

Abstract: A data management system or “DMS” provides an automated, continuous, real-time, substantially no downtime data protection service to one or more data sources associated with a set of application host servers. To facilitate the data protection service, a host driver embedded in an application server captures real-time data transactions, preferably in the form of an event journal that is provided to other DMS components. The driver functions to translate traditional file/database/block I/O and the like into a continuous, application-aware, output data stream. The host driver includes an event processor. When an authorized user determines that a primary copy of the data in the host server has become incorrect or corrupted, the event processor can perform a recovery operation to an entire data source or a subset of the data source using former point-in-time data in the DMS. The recovery operation may have two phases.

Abstract: A data management system or “DMS” provides data services to data sources associated with a set of application host servers. The data management system typically comprises one or more regions, with each region having one or more clusters. A given cluster has one or more nodes that share storage. When providing continuous data protection and data distribution, the DMS nodes create distributed object storage to provide the necessary real-time data management services. The objects created by the DMS nodes are so-called active objects. The distributed object store can be built above raw storage devices, a traditional file system, a special purpose file system, a clustered file system, a database, and so on. According to the present invention, the DMS active object store provides an indexing service to the active objects. In an illustrative embodiment, any object property that has a given attribute is indexed and, as a result, the attribute becomes searchable.

Abstract: A “forward” delta data management technique uses a “sparse” index associated with a delta file to achieve both delta management efficiency and to eliminate read latency while accessing history data. The invention may be implemented advantageously in a data management system that provides real-time data services to data sources associated with a set of application host servers. To facilitate a given data service, a host driver embedded in an application server connects an application and its data to a cluster. The host driver captures real-time data transactions, preferably in the form of an event journal that is provided to the data management system. In particular, the driver functions to translate traditional file/database/block I/O into a continuous, application-aware, output data stream.

Abstract: A method and apparatus for controlling the parking of a transducer head in a disk drive. A drive current is provided to a motor which controls movement of the head in a direction to move the head to a parking position. The arrival of the head at the parking position is detected. Upon this detection, a drive stop sequence is initiated to stop providing the drive current a short time after the head reaches the parking position. In one embodiment, it is determined whether the head has reached the parking position by monitoring the back emf (bemf) of the motor controlling the head, typically a voice coil motor (VCM). The detection of a sharp decline in the bemf indicates the head has stopped.

Abstract: A circuit for controlling a voice-coil motor (VCM) may incorporate a pulse-width modulation driver to drive the VCM, a zero-current detector to determine whether the current across the VCM is zero, and a Back-EMF voltage detector to measure the voltage across the VCM when the current across the VCM is determined to be zero. The circuit may determine the current velocity of the VCM and use this information to control the velocity of the VCM.

Abstract: A data management system that protects data into a continuous object store includes a management interface having a time control. The time control allows an administrator to specify a “past” time, such as a single point or range. When the time control is set to a single point, a hierarchical display of data appears on a display exactly as the data existed in the system at that moment in the past. The time control enables the management interface to operate within a history mode in which the display provides a visual representation of a “virtual” point in time in the past during which the data management system has been operative to provide the data protection service.

Abstract: Analog control of the pulse width used to control the speed of a voice coil motor may be implemented using a “constant-current-charging-capacitor” configuration where the time needed to charge the capacitor is directly related to how far the actual motor speed is from the target speed. The BEMF voltage, indicative of motor speed, is sampled, and then stored in a storage capacitor, which is allowed to charge/discharge to a target voltage level. The time required to charge/discharge the capacitor to the target voltage is directly proportional to the difference between the BEMF voltage and the target voltage, and may be used directly as the pulse width (i.e., the charging time) in the PWM velocity control system. To avoid larger capacitors, a pulse multiplier circuit can be added, allowing charging/discharging the sampled voltage to the target voltage to be repeated by a number, N, of times.

Abstract: The power required by a voice coil motor (VCM) to maintain the head in the data region of a disk drive during an idle mode is further reduced. The current supplied to the VCM is switched on and off. This takes advantage of the inherent inductance in the VCM, which maintains a current after the current supply is switched off. The current will slowly decay, with it being switched on again before it reaches a level where the average value won't offset the flex bias. In one embodiment, the current is maintained in a single direction, to offset the flex bias which pushes in one direction. Digital switches are used to reduce the power consumption of the control circuitry.

Abstract: A circuit system and process utilizes back electromotive force (BEMF) voltage to assist in safe power down of devices, such as the read/write head in from low factor disk drives or similar devices. The BEMF voltage from a motor device, such as a spindle motor utilized in a circuit using negative voltage to drive some switches, such as positive channel metal oxide semiconductor (“PMOS”) driver transistors, to reduce and/or effectively minimize the on-resistance of the switches while delivering the current from BEMF voltage of the motor to another device, such as a motor that retracts controls a read/write head.

Abstract: A data management system or “DMS” provides an automated, continuous, real-time, substantially no downtime data protection service to one or more data sources associated with a set of application host servers. To facilitate the data protection service, a host driver embedded in an application server captures real-time data transactions, preferably in the form of an event journal that is provided to other DMS components. The driver functions to translate traditional file/database/block I/O and the like into a continuous, application-aware, output data stream. The host driver includes an event processor. When an authorized user determines that a primary copy of the data in the host server has become incorrect or corrupted, the event processor can perform a recovery operation to an entire data source or a subset of the data source using former point-in-time data in the DMS. The recovery operation may have two phases.

Abstract: A data management system or “DMS” provides an automated, continuous, real-time data protection service to one or more data sources associated with a set of application host serves. To facilitate the service, a host driver embedded in an application server captures real-time data transactions. When a data protection command for a given data source is forwarded to a host driver, an event processor enters into an initial upload state. During this state, the event processor gathers a list of data items to be protected and creates a data list. Then, the event processor moves the data to a DMS core to create initial baseline data. The upload is a stream of application-aware data chunks that are attached to upload events. A resynchronization state is entered when there is a suspicion that the state of the data in the host is out-of-sync with the state of the most current data in the DMS.

Abstract: An efficient method to apply an erasure encoding and decoding scheme across dispersed data stores that receive constant updates. A data store is a persistent memory for storing a data block. Such data stores include, without limitation, a group of disks, a group of disk arrays, or the like. An encoding process applies a sequencing method to assign a sequence number to each data and checksum block as they are modified and updated onto their data stores. The method preferably uses the sequence number to identify data set consistency. The sequencing method allows for self-healing of each individual data store, and it maintains data consistency and correctness within a data block and among a group of data blocks. The inventive technique can be applied on many forms of distributed persistent data stores to provide failure resiliency and to maintain data consistency and correctness.