Abstract: A method and apparatus for cache coherency in storage system is disclosed. The invention maintains cache coherency in the controller system of the storage system in a manner to minimize the performance degradation to a host system, and to allow the caches to be coherent without requiring data to be written to the backing disks. Each controller manages an area of memory on the partner controller, but the area is managed dynamically and is done with the information about the partner controller. A first controller determines which mirror cache line on a second controller to copy data into, and then mirrors the data from a first controller cache line to a second controller cache line. A message is sent from the first controller to the second controller informing the second controller of cache meta data associated with the mirror cache line so that the cache line may be added to the second controller's hash table.

Abstract: Disclosed is a system and a method for implementing trace buffers in a computer program. A trace facility monitors operation of the computer program in real time. As the code is executed, error-related events occur and are divided into at least three components, including errors, warnings, and messages. Records of these events are stored in the trace buffers. Each task, process, or component of the embedded system that is traced may have an independent set of trace buffers. Unique events eliminate the confusion as to where or when an event occurs in a system. Separate trace buffers for each component of the embedded system ensure that no component consumes buffer resources needed by other components. The trace facility may be embedded in the code in a transparent manner and may be utilized to locate errors on-site.

Abstract: A method and apparatus for quiescing a system storage device wherein cache lines associated with a system storage device to be quiesced are flushed using a stripe lock mechanism to find and flush cache data associated with the given system storage device. Dirty cache lines are associated with a stripe lock, and that stripe lock will be in the active state or the clearing state. The stripe locks are also maintained on a linked list per a system storage device. In the normal life cycle of a stripe lock, if the partner controller requests a lock over part of the extent of an active lock, the active lock will go to the clearing state. Data in the extent of the now clearing lock is flushed. For performing a quiesce, stripe locks for the given system storage device are set to clearing on a plurality of controllers, thus causing the flush. The quiesce mechanism then only needs to wait until stripe locks have been cleared for the system storage device.

Abstract: A method, computer readable medium, apparatus and RAID controller for performing nondestructive write testing is disclosed. For data storage devices divided into sectors, the present invention performs nondestructive write testing by writing data to the sectors, reading data written to the sectors, and comparing the data written to the data read to detect errors. To increase efficiency, sectors previously written by a host or other computer are tracked, allowing sectors not previously written to be tested without saving and restoring data in the sectors. To locate the sectors written to by the host computer, write indicators such as a sector written indicator, a sector stripe written indicator, and a stripe written indicator are maintained. Upon detecting a defective sector, a new sector is allocated, and the defective sector is replaced by the allocated sector.

Abstract: A data storage system that includes computer coupled to disk array controller which is coupled to data storage devices. First procedure provides a method to perform data consistency checking and correction of user data stored in data sectors on a data stripe. Each data sector includes data header and data stripe includes a parity sector, and parity sector includes a parity header. Data stripe is distributed across storage devices. Provides each data header with first code to provide a check for the user data stored in the data header's data segment, provides the parity header with second code to provide a check for a set of parity data stored in parity sector, and provides the parity header with third code by encoding each respective first code with second code. Third code enables user to check consistency of user data and parity data without respective operations on each byte of data in both data sectors and parity sector.

Abstract: Whenever a controller receives a message that includes a particular target ID and a particular computer's operating requirements with respect to the operation of the plurality of logical units mapped across a plurality of disk storage devices, the controller stores one set of the particular computer's operating requirements per target ID per logical unit. Each host computer in a data storage system that has substantially similar operating requirements uses the same target ID in any I/O requests to a controller. Subsequently, whenever the controller processes an I/O request from any computer that uses the particular target ID, the controller will use the particular set of the operating requirements to configure the operation of each of the logical units.