A storage subsystem monitors one or more conditions related to the probability of a data error occurring. Based on the monitored condition or conditions, the storage subsystem adjusts an error correction setting, and thus the quantity of ECC data used to protect data received from a host system. To enable blocks of data to be properly checked when read from memory, the storage subsystem stores ECC metadata indicating the particular error correction setting used to store particular blocks of data. The storage subsystem may be in the form of a solid-state non-volatile memory card or drive that attaches to the host system.

Storage subsystem capable of adjusting ecc settings based on monitored conditions

A proactive, resilient and self-tuning memory management system and method that result in actual and perceived performance improvements in memory management, by loading and maintaining data that is likely to be needed into memory, before the data is actually needed. The system includes mechanisms directed towards historical memory usage monitoring, memory usage analysis, refreshing memory with highly-valued (e.g., highly utilized) pages, I/O pre-fetching efficiency, and aggressive disk management. Based on the memory usage information, pages are prioritized with relative values, and mechanisms work to pre-fetch and/or maintain the more valuable pages in memory. Pages are pre-fetched and maintained in a prioritized standby page set that includes a number of subsets, by which more valuable pages remain in memory over less valuable pages. Valuable data that is paged out may be automatically brought back, in a resilient manner. Benefits include significantly reducing or even eliminating disk I/O due to memory page faults.

Methods and mechanisms for proactive memory management

Data storage media, such as silicon-based non-volatile memory, are configured according to a data structure containing a payload portion and a redundancy portion. A divider segregating the payload and redundancy portions may be dynamically relocated, thereby altering the size of the redundancy to allow for use of an error correcting code selected to provide the data integrity required in response to changing conditions.

Dynamic variable-length error correction code

A data processing system includes a first storage system that is connected to a host device and sends and receives data to and from the host device; a second storage system that is connected to the first storage system and receives data from the first storage system; and a third storage system that is connected to the first storage system and receives data from the first storage system. The first storage system, the second storage system and the third storage system are arranged to be changeable between a first status including first and second copy pairs and a second status including a third copy pair in response to a predetermined condition at the first storage system.

Data processing system

A disk drive is disclosed for executing a preemptive multitasking operating system comprising tasks of varying priority, including a disk task for processing disk commands by initiating seek operations and configuring parameters of a read/write channel, a host task for initiating disk commands in response to host commands received from a host computer, a background task for initiating disk commands to perform background operations including a defect scan of the disk, and an execution task for arbitrating the disk commands generated by the host task and the background task and for transmitting the arbitrated disk commands to the disk task.

Disk drive executing a preemptive multitasking operating system comprising tasks of varying priority

A cooperative disk cache management and rotational positioning optimization (RPO) method for a data storage device, such as a disk drive, makes cache decisions that decrease the total access times for all data The cache memory provides temporary storage for data either to be written to disk or that has been read from disk Data access times from cache are significantly lower than data access times from the storage device, and it is advantageous to store in cache data that is likely to be referenced again For each data block that is a candidate to store in cache, a cost function is calculated and compared with analogous cost functions for data already in cache The data having the lowest cost function is removed from cache and replaced with data having a higher cost function The cost function C measures the expected additional cost, in time, of not storing the data in cache, and is given by C=(T d −T c )P, where T d is the disk access time, T c is the cache access time, and P is an access probability for the data Access times are calculated according to an RPO algorithm that includes both seek times and rotational latencies

Cooperative cache and rotational positioning optimization (RPO) scheme for a direct access storage device (DASD)

Disclosed is a system, method, and program for selecting an input/output (I/O) command in a queue of I/O commands. Each I/O command operates within a range of addressable locations on a storage medium. Each addressable location is defined according to a sector number and track number. The program makes use of a plurality of buckets, wherein each bucket represents a range of consecutive sector numbers. Each queued I/O command is associated with a bucket such that a sector number of an addressable location in which an I/O command operates is within the range of sectors comprising the associated bucket. A reference position is determined. A selection routine is then executed to select an I/O command. The selection routine selects a bucket including at least one I/O command and selects an I/O command within the selected bucket. The routine then determines whether the selected I/O command meets a selection criteria. The routine indicates the selected I/O command as the I/O command to process. Another iteration of the selection routine is performed after determining that the selected I/O command does not meet the selection criteria.

Method, system, and program for reordering a queue of input/output (I/O) commands into buckets defining ranges of consecutive sector numbers in a storage medium and performing iterations of a selection routine to select and I/O command to execute

Provided are a method, system, and program for performing error correction in a storage device having a magnetic storage medium. A plurality of zones are defined in the magnetic storage medium, wherein each zone comprises a plurality of addressable locations in the magnetic storage medium. A determination is made as to whether a change of a signal-to-noise ratio for one subject zone of the plurality of zones exceeds a threshold. An operation is performed to improve the signal-to-noise ratio with respect to the subject zone of the magnetic storage medium after determining that the change of the signal-to-noise ratio exceeds the threshold.

Method, system, and program for performing error correction in a storage device having a magnetic storage medium

A disk drive operative to reduce squeeze hard error is described. In response to a write fault ( 404 ) indicating that data has been inadvertently written to some portion of a track adjacent to an intended track, track overshoot is determined ( 416 ) based on a position error signal (PES) and pre-stored head width data. If the track overshoot exceeds a threshold ( 418 ), data from the adjacent track is read and rewritten ( 422 ) to remove the overshoot interference. Preferably, the reading and rewriting is performed during an idle mode immediately following the write fault using previously stored addresses.

Method of and apparatus for improving data integrity in a disk drive system

Linearity compensation is provided for a position error signal based on repeatable and non-repeatable run out in a data storage device. The run out is measured on a track of the data storage device at a plurality of points, such as a track center and one or more points offset from the track center. The run out is typically measured using either an unstitched primary position error signal or an unstitched quadrature position error signal. The offsets are usually stitch points for the position error signal. A component of the run out is extracted at the points, wherein the component generally comprises one or more characteristics of the run out, such as a frequency, a set of frequencies, a root mean square, or some other characteristic of the run out. The linearizing equation to be used for the position error signal is identified based on the measured run out and generally comprises a polynomial function. The coefficients of the linearizing equation are adjusted so that the run out and the component of the run out are substantially similar at the points. These steps are repeated until a satisfactory fit is achieved in the linearizing equation. Once a satisfactory fit is achieved, the coefficients for the linearizing equation are stored in the data storage device, so that they can be accessed by a servo controller during operation of the data storage device. The servo controller uses the linearizing equation to generate a linearized position error signal that is used to improve a track following capability of the data storage device.

Bernd Lamberts

Papers

Cooperative cache and rotational positioning optimization (RPO) scheme for a direct access storage device (DASD)

Method, system, and program for reordering a queue of input/output (I/O) commands into buckets defining ranges of consecutive sector numbers in a storage medium and performing iterations of a selection routine to select and I/O command to execute

Method, system, and program for performing error correction in a storage device having a magnetic storage medium

Method of and apparatus for improving data integrity in a disk drive system

Linearity compensation for a position error signal based on repeatable and non-repeatable run out in a disk drive