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: 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 voltage tripler circuit includes a plurality of switches and first, second, and third capacitors each having first and second terminals that are selectively interconnected via the plurality of switches. The first capacitor charges to a supply voltage during a first phase. The second capacitor charges to two times the supply voltage during a second phase that follows the first phase. The third capacitor charges to three times the supply voltage during a third phase that follows the second phase. The voltage tripler circuit draws the same peak current from a source of the supply voltage at a beginning of each of the first, second, third 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 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 servers. 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. During upload or upward resynchronization, the application does not have to be shut down.

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: 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: 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: 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 charging system includes a current source, a voltage pump, and a comparator that compares a charging level of a capacitor to each of a first threshold and a second threshold. A controller turns on the voltage pump and turns off the current source after the charging level exceeds the first threshold, and turns off the voltage pump and turns on the current source when the charging level falls below the second threshold. The first threshold is greater than the second threshold.

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 system includes a current control module that supplies current to a voice coil motor during a first period to rotate an actuator arm in a first rotational direction, that discharges the current from the voice coil motor after the first period, and that generates a control signal a predetermined period after the current is discharged. A back electromagnetic force (bemf) module generates a bemf signal in response to the control signal. A speed control module determines a speed of the actuator arm based on the bemf signal.

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: 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 a data protection command for a given data source is forwarded to a host driver, the event processor enters into an initial upload state. During this state, the event processor gathers a list of data items of the data source to be protected and creates a data list. Then, the event processor moves the data (as an upload, preferably one data element at a time) to a DMS core to create initial baseline data.

Abstract: In a method for measuring motor speed and position by detecting the back-EMF generated during pole-pair interactions, fluctuations of a three-phase motor power supply that may affect back-EMF detection are reduced. One phase of the power supply is tristated for a certain interval preceding and during back-EMF detection. For a shorter interval during back-EMF detection, the voltage drop across the motor is reduced from the full power supply voltage. This preferably is accomplished either by pulling a first of the other two power supply phases low, while pulling a second of the other two power supply phases up to a regulated voltage below the power supply voltage, or by pulling the second of the other two phases up to the power supply voltage and pulling the first of the other two phases down to a regulated voltage above ground.

Abstract: A three-phase voltage tripler includes first, second, and third capacitive elements and a switching module. The switching module selectively switches connections among the capacitive elements and between the capacitive elements and a reference voltage during first, second, and third periods. The switching module charges the first capacitive element to a first voltage level during the first period, the second capacitive element to a second voltage level during the second period, and the third capacitive element to a third voltage level during the third period. The third voltage level is greater than the second voltage level and the second voltage level is greater than the first voltage level.

Abstract: A system and method for controlling an actuator includes a control module that communicates with a plurality of switching devices to generate current through a voice coil motor during a first time period so that an actuator arm rotates in a first rotational direction in response to the current. The control module controls the switching devices to discharge the current from the voice coil motor during a second time period less than the first time period so that the first rotational direction of the actuator arm is maintained after discharging the current. The control module further includes a back electromagnetic force (bemf) module for determining a bemf voltage after controlling the switching devices to discharge the current, and an actuator arm speed control module for determining an actuator arm speed in response to the bemf voltage.

Abstract: Circuits and methods are provided for producing a rail-to-rail output voltage. A circuit includes a level shifter and a source follower. The level shifter receives an input signal and applies a compensation voltage to the input signal relative to a voltage level of the input signal in steady-state. The source follower produces an output signal and, responsive to variations in the voltage level of the input signal, changes the voltage level of the output signal.

Abstract: A data management system (DMS) includes a continuous real-time object store that captures all real-time activities, with associated object metadata information. The DMS is capable of reintroducing any point-in-time view of data ranging from a granular object to an entire file system. A set of algorithms (for creation of a file or directory, modification of a file or directory, deletion of a file or directory, and relocation/renaming of a file or directory) are used to generate and maintain a file system history in the DMS and to ensure that a latest version of a directory always refers to a latest version of its children until the directory changed. Any point-in-time recovery is implemented using the file system history in one of various ways to provide strong individual file integrity, exact point-in-time crash consistency, and/or recovery of last version of all files in the file system.