Abstract: An improved technique for storing I/O metrics includes assigning metric values to data buckets held in kernel memory. Each data bucket covers a particular range of values of a respective metric and is configured as a counter, whose count is incremented each time the multipathing driver obtains or computes a metric value that falls within the range of the data bucket. Bucket counts can be read by an external program to obtain aggregate information about I/O metrics over time. The aggregate information can be fed back to the multipathing driver to enable improved selections of paths for conveying data to and from a storage array.

Abstract: An improved technique for handling events in a multipathing driver employs an event queue and a queue manager that run in the kernel of a computing system. The queue manager receives events raised by the multipathing driver, as well as events raised by software constructs, such as application programs. Records of events are added to the event queue in the order the queue manager receives them. Event records may be consumed chronologically by external software. Preferably, the event queue is sufficiently large to store all events arising out of most predicted fault scenarios. Also, the queue manager is sophisticated and can perform certain diagnostic and analysis tasks without the aid of external software.

Abstract: An improved technique for storing I/O metrics includes assigning metric values to data buckets held in kernel memory. Each data bucket covers a particular range of values of a respective metric and is configured as a counter, whose count is incremented each time the multipathing driver obtains or computes a metric value that falls within the range of the data bucket. Bucket counts can be read by an external program to obtain aggregate information about I/O metrics over time. The aggregate information can be fed back to the multipathing driver to enable improved selections of paths for conveying data to and from a storage array.

Abstract: An improved technique for handling events in a multipathing driver employs an event queue and a queue manager that run in the kernel of a computing system. The queue manager receives events raised by the multipathing driver, as well as events raised by software constructs, such as application programs. Records of events are added to the event queue in the order the queue manager receives them. Event records may be consumed chronologically by external software. Preferably, the event queue is sufficiently large to store all events arising out of most predicted fault scenarios. Also, the queue manager is sophisticated and can perform certain diagnostic and analysis tasks without the aid of external software.

Abstract: The present invention provides a method for applying a tribological coating to a carbon composite substrate. The method includes providing the carbon composite substrate, depositing a layer of carbon on the substrate, applying a layer of aluminum on the layer of carbon, annealing the substrate at a temperature greater than a melting temperature of aluminum, and applying a layer of silver. A layer of mixed aluminum and silver may be substituted for the layer of silver.

Abstract: A read servo mechanism that uses levels of read data signal quality to maintain track centerline is presented. In a seek operation mode, a baseline signal quality value is sampled at a current tracking position and, once the baseline signal quality value is established, the head is stepped to change its position and the signal quality value sampled after each position change to determine change in signal quality until the change in signal quality is found to be insignificant. After a predetermined interval, the signal quality value is again sampled. If the signal quality value has changed significantly or the time that has expired since the seek operation mode ended is greater than some larger interval, the seek operation is repeated in an effort to search for a new baseline level of signal quality (and, therefore, the new track center).

Abstract: A read servo mechanism that uses levels of read data signal quality to maintain track centerline is presented. In a seek operation mode, a baseline signal quality value is sampled at a current tracking position and, once the baseline signal quality value is established, the head is stepped to change its position and the signal quality value sampled after each position change to determine change in signal quality until the change in signal quality is found to be insignificant. After a predetermined interval, the signal quality value is again sampled. If the signal quality value has changed significantly or the time that has expired since the seek operation mode ended is greater than some larger interval, the seek operation is repeated in an effort to search for a new baseline level of signal quality (and, therefore, the new track center).