Abstract: A method and apparatus for enabling an on-line reconfiguration of striped data in a disk array storage device. A replicated copy of the striped logical device is made in parallel with host operations. A logical device with a new configuration is then substituted for access by the host application even before any data is transferred to locations within the newly configured logical device. Independent processes operating in this disk array storage device reconfigure the data transparently to any host operations while accommodating host I/O requests directed to locations in the new configuration.

Abstract: A method and apparatus for enabling an on-line reconfiguration of striped data in a disk array storage device. A replicated copy of the striped logical device is made in parallel with host operations. A logical device with a new configuration is then substituted for access by the host application even before any data is transferred to locations within the newly configured logical device. Independent processes operating in this disk array storage device reconfigure the data transparently to any host operations while accommodating host I/O requests directed to locations in the new configuration.

Abstract: A method and apparatus for enabling an on-line reconfiguration of striped data in a disk array storage device. A replicated copy of the striped logical device is made in parallel with host operations. A logical device with a new configuration is then substituted for access by the host application even before any data is transferred to locations within the newly configured logical device. Independent processes operating in this disk array storage device reconfigure the data transparently to any host operations while accommodating host I/O requests directed to locations in the new configuration.

Abstract: A method and apparatus for enabling an on-line reconfiguration of striped data in a disk array storage device. A replicated copy of the striped logical device is made in parallel with host operations. A logical device with a new configuration is then substituted for access by the host application even before any data is transferred to locations within the newly configured logical device. Independent processes operating in this disk array storage device reconfigure the data transparently to any host operations while accommodating host I/O requests directed to locations in the new configuration.

Abstract: A method and apparatus for enabling an on-line reconfiguration of striped data in a disk array storage device. A replicated copy of the striped logical device is made in parallel with host operations. A logical device with a new configuration is then substituted for access by the host application even before any data is transferred to locations within the newly configured logical device. Independent processes operating in this disk array storage device reconfigure the data transparently to any host operations while accommodating host I/O requests directed to locations in the new configuration.

Abstract: A method and data storage system using the method, provides an efficiently approach for allocating a static amount of buffer space (e.g., records) among a number of logical volumes of a data storage system on the basis of the computing environment within which the data storage system is used. The method includes providing the data storage system from logical volumes, each including a command queue. Each command queue includes records, each for storing a command request. A memory pool is established from which one or more records can be allocated to each command queue associated with each logical volume. The memory pool has a predetermined number of records which can be allocated by the command queues of the logical volumes. Based on the computing environment, one of a number of allocation schemes for allocating records to a command queue is selected.

Abstract: A method and apparatus for providing very large logical volumes (Meta Device) in a storage system is provided. The storage system includes host controllers and disk controllers which communicate through a shared memory. I/O requests are received by the host controller and placed into request queues. The request queues are associated with logical devices. A number of request queues in the host controller are concatenated together to produce the larger logical volume. The large logical volume appears to the host as a single addressable logical unit. I/O requests to the large logical volume are analyzed by the host controller to determine which logical devices are actually needed to service the request. The host controller then makes the appropriate queue entries. Processing of the requests then occurs in the same fashion as if the request had been to a non-Meta Device. This allows the disk controllers and memory to operate without modification.

Abstract: A method of dynamically reconfiguring the logical devices in a storage system is provided. The method allows a logical devices to be added, removed, or repositioned without requiring the storage system to be taken off-line. The method includes manipulating the request queues associated with host controllers within the storage system. The request queues associated with each logical device may be repositioned in the request queue memory in order to make room for new logical devices or to take advantage of free space associated with a removed logical device. The storage system communicates with the host computer in order to manage the reconfiguration of the request queues while still providing storage services to the host computer.

Abstract: A method and apparatus for providing very large logical volumes (Meta Device) in a storage system is provided. The storage system includes host controllers and disk controllers which communicate through a shared memory. I/O requests are received by the host controller and placed into request queues. The request queues are associated with logical devices. A number of request queues in the host controller are concatenated together to produce the larger logical volume. The large logical volume appears to the host as a single addressable logical unit. I/O requests to the large logical volume are analyzed by the host controller to determine which logical devices are actually needed to service the request. The host controller then makes the appropriate queue entries. Processing of the requests then occurs in the same fashion as if the request had been to a non-Meta Device. This allows the disk controllers and memory to operate without modification.

Abstract: A method and apparatus provide input/output allocation between a host and a data storage system. Input/output allocation is accomplished by organizing logical volumes (e.g., disk drives) in the data storage system and queuing requests to the data storage system in a manner which increases the speed and throughput of input/output (I/O) operations. The data storage system is provided from a plurality of logical volumes, each of the logical volumes including a command queue. A master command queue is established from one of the command queues of the logical volumes. The master command queue receives command requests from the host, each command request including an address of data being requested. Each command request is received from the host and stored in the master command queue. The logical volume where the address of the data associated with each command request resides is determined. Each command request is then forwarded to the logical volume where the data being requested resides.

Abstract: A method of improving the performance of a storage system is provided. The method includes sending a pre-request to a logical device before data associated with the previous request is transferred from a cache to the requesting host device. Additionally, while a host controller of the storage system is transferring data from the cache to the requesting host, it will also check to see if any other requests are entered in a request queue for that logical device. To do this, the host controller checks a status flag in a mailbox location within the host controller. A disk controller is also responsive to the placement of requests in the mailbox location and can set the status flag upon a completion of a data transaction. If there has been an entry, a pre-request will be sent to the logical device while the data from the previous request is being transferred to the host.