Abstract: A method, system, and computer program product for providing continuous data protection for write data supplied from a host incorporating a processor device to data storage in accordance with write input/output (I/O) of an owning application is provided. The write data is identified as one of a synchronous candidate and an asynchronous candidate. The write data identified as the one of the synchronous candidate and the asynchronous candidate is transferred to at least one sidefile. The write data transferred to the at least one sidefile is secured in a nonvolatile storage journal. The nonvolatile storage journal is preset with a timeout limit applicable to write data identified as the synchronous candidate. If the timeout limit is exceeded, a loss mitigation operation to safeguard the write data identified as the synchronous candidate is performed.

Abstract: A method, system, and computer program product for providing continuous data protection for write data supplied from a host incorporating a processor device to data storage in accordance with write input/output (I/O) of an owning application is provided. The write data is identified as one of a synchronous candidate and an asynchronous candidate. The write data identified as the one of the synchronous candidate and the asynchronous candidate is transferred to at least one sidefile. The write data transferred to the at least one sidefile is secured in a nonvolatile storage journal. The nonvolatile storage journal is preset with a timeout limit applicable to write data identified as the synchronous candidate. If the timeout limit is exceeded, a loss mitigation operation to safeguard the write data identified as the synchronous candidate is performed.

Abstract: An apparatus, system, and method are disclosed for switching a volume address association in a point-in-time copy relationship. A copy module creates a point-in-time copy structure of a source volume at a target volume. A migration module copies data from the source volume to the target volume. A detection module detects data corruption in the source volume. A switch module switches a logical volume address from a source volume address of the source volume to a target volume address of the target volume in response to detecting the data corruption, redirecting data reads and writes to the target volume. In one embodiment, a tracking module tracks a current target volume copy of source volume data and redirects an access for source volume data without the current target volume copy to the source volume.

Abstract: A data recording disk file with a voice coil motor (VCM) actuator and a digital servo control system for positioning the read/write heads to selected concentric data tracks includes means for calculating the factor relating acceleration of the heads to VCM input current. This permits each disk file to compensate for any variation in the nominal VCM physical parameters, thus enabling VCMs to be manufactured to less demanding tolerances. The disk file also calculates a unique acceleration factor for each head position during movement of the heads from one track to another, thereby improving the arrival time of the heads to the target track. During an initialization procedure, the disk file performs a track seek, during which VCM current and head velocity information are acquired and used by the microprocessor in the digital servo control system to calculate a value representing an average actual acceleration factor unique to that disk file.

Abstract: A disk file digital servo control system incorporates means for measuring the time between samples of read/write head position error signals (PES), and uses a value of that measured time as part of the computation of the digital control signal. The digital servo control system has a microprocessor which runs a control signal algorithm, a portion of which is a state estimator for estimating the position, velocity and acceleration of the head. The state estimator requires the use of estimator constants determined from physical parameters of the disk file, including the PES sampling time. By using the actual measured PES sampling time, rather than a constant value of nominal PES sampling time, the estimator constants can be modified to improve the accuracy of the computed control signal. This results in improved performance of the control system to move the head to the target track whenever there are variations in the nominal PES sampling time caused by variations in the disk file drive motor speed.