Lsi Logic Corporation

Symbios Logic Inc.

Hyundai Electronics America, Inc.

At&t Global Information Solutions Company

Michael J Gallagher

Charles D Binford

Ray M Jantz

Craig C McCombs

Rodney A DeKoning

In a storage environment or storage area network having multiple host devices and at least one storage array, the host devices access logical data volumes stored on the storage array through array controllers disposed in the storage array. Multiple host devices can request access to shared ones of the logical data volumes through multiple paths to multiple array controllers, but each logical data volume is controlled or owned by only one array controller at a time. Thus, ownership of shared logical data volumes is transferred between the array controllers as necessary on behalf of the requesting host devices. To prevent ownership transfers from occurring too often, however, ownership of the logical data volumes is made exclusive, or &ldquo;sticky,&rdquo; for a period of time after each transfer. During the exclusive ownership period of time, the ownership cannot be transferred. After expiration of the exclusive ownership period of time, ownership of the affected logical data volume is transferred if the transfer does not cause another host device to lose access to the same logical data volume, unless priorities between competing host devices permit one host device to take access away from the other host device.

Method and apparatus for handling transfers of data volumes between controllers in a storage environment having multiple paths to the data volumes

Apparatus and associated methods for improving I/O performance in a computing system which includes one or more MPUs and one or more IOPs. I/O requests are queued by a requesting MPU in a memory shared with one or more IOPs. Each IOP is associated with a queue. Each IOP may continue processing queued I/O requests after completing processing on an earlier request. In addition, each MPU is associated with a queue shared with the IOPs. When an IOP completes processing of an I/O request, a completion message is added to the requesting MPU's queue and an interrupt is generated for that MPU. The MPU services all completion messages in its queue when the interrupt is processed. A threshold value is associated with each MPU queue. The threshold value indicates the minimum number of completed I/O requests required before an interrupt request is generated to the MPU. The threshold value for each MPU may be tuned to permit the computing system to balance the need for rapid I/O response time with the need for reduced interrupt overhead processing in the MPU. Various physical embodiments of the invention are disclosed wherein the queue is located in either a shared memory or in a register file. Additionally, various embodiments separate the queue used to store new I/O requests from the queue used to store completion messages while other embodiments merge the two queuing functions into a single queue where each entry contains an I/O request with a completion status field.

Employing request queues and completion queues between main processors

I/O system for reducing main processor overhead in initiating I/O

A procedure for scheduling multiple process requests for read/write access to a disk memory device within a computer system. The procedure considers disk characteristics, such as the number of sectors per track, the number of tracks per cylinder, speed of disk rotation and disk controller queuing capability in determining the optimal order for executing process requests. Process requests are placed in packets within an execution queue, each packet including up to a predetermined maximum number of requests. Within the packets, the process requests are sorted in ascending/descending order by the cylinder number to which the requests desire access, while within each cylinder the requests are placed in next-closest-in-time sequence.

Method for scheduling the execution of disk I/O operations

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Wichita, KS, United States of America

Michael J Gallagher