Abstract: A very large virtual volume (e.g., in excess of 500 GB) is formed by distributing the disks in eleven, six-disk RAID-5 sets across the six busses of a primary local back-end controller. A spare disk is provided on each of the six busses. Each RAID-5 set is protected from the failure of a single disk by the spare disks on the busses, which can use the parity data stored in a RAID-5 set to rebuild the data stored on a failing disk and thereby restore redundancy to the RAID-5 set. Each RAID-5 set is also protected from the failure of a bus by the parity inherent in RAID-5. The RAID-5 sets are striped by a front-end controller connected to the primary local back-end controller, and the striped RAID-5 sets are presented to a host computer as a very large virtual volume. If the individual disks are 9.1 GB in size, the size of the very large virtual volume can reach 500.5 GB.

Abstract: A method of managing storage comprises connecting a number of virtual disks to a disk controller loop of a disk controller, and mounting a portion of the number of virtual disks to the disk controller wherein a storage map is loaded into a fixed-size memory of the disk controller for each virtual disk mounted. The method further comprises receiving a request for data contained on an unmounted virtual disk with the unmounted virtual disk having a storage map of certain size. A sufficient number of mounted virtual disks are dismounted to allow the fixed-size memory to accommodate the certain size of the unmounted virtual disk storage map. The unmounted virtual disk may be mounted.

Abstract: A method of managing storage comprises connecting a number of virtual disks to a disk controller loop of a disk controller, and mounting a portion of the number of virtual disks to the disk controller wherein a storage map is loaded into a fixed-size memory of the disk controller for each virtual disk mounted. The method further comprises receiving a request for data contained on an unmounted virtual disk with the unmounted virtual disk having a storage map of certain size. A sufficient number of mounted virtual disks are dismounted to allow the fixed-size memory to accommodate the certain size of the unmounted virtual disk storage map. The unmounted virtual disk may be mounted.

Abstract: In a storage apparatus, a logic is adapted to write to disk group metadata information including state information that self-identifies state of the disk group and enables a disk controller to load and present virtual disks corresponding to the disk group as logical units to a client in the absence of disk group state information contained in the disk controller.

Abstract: A very large virtual volume (e.g., in excess of 500 GB) is formed by distributing the disks in eleven, six-disk RAID-5 sets across the six busses of a primary local back-end controller. A spare disk is provided on each of the six busses. Each RAID-5 set is protected from the failure of a single disk by the spare disks on the busses, which can use the parity data stored in a RAID-5 set to rebuild the data stored on a failing disk and thereby restore redundancy to the RAID-5 set. Each RAID-5 set is also protected from the failure of a bus by the parity inherent in RAID-5. The RAID-5 sets are striped by a front-end controller connected to the primary local back-end controller, and the striped RAID-5 sets are presented to a host computer as a very large virtual volume. If the individual disks are 9.1 GB in size, the size of the very large virtual volume can reach 500.5 GB.

Abstract: A very large virtual storage volume formed by distributing disks in multiple, multi-disk RAID (redundant array of independent disks) sets across busses of a back-end controller. The multiple RAID sets are striped by a front-end controller connected to the back-end controller and presented to a host computer as a very large virtual storage volume.

Abstract: A system for generating a virtual point-in-time copy of a selected subset (e.g., a selected volume or logical unit) of a storage system. The present system operates by using a bitmap in storage system controller cache memory to indicate blocks of memory in the selected volume that have been overwritten since the snapshot was initiated. When a write to the selected volume is requested, the cache bitmap is checked to determine whether the original data (in the area to be overwritten) has already been copied from the selected volume to a temporary volume. If the original data was previously copied, then the write proceeds to the selected volume. If, however, the original data would be overwritten by the presently requested write operation, then an area containing the original data is copied from the selected volume to a temporary volume. Reads from the temporary volume first check the bitmap to determine if the requested data has already been copied from the selected volume to the temporary volume.

Abstract: A very large virtual volume (e.g., in excess of 500 GB) is formed by distributing the disks in eleven, six-disk RAID-5 sets across the six busses of a primary local back-end controller. A spare disk is provided on each of the six busses. Each RAID-5 set is protected from the failure of a single disk by the spare disks on the busses, which can use the parity data stored in a RAID-5 set to rebuild the data stored on a failing disk and thereby restore redundancy to the RAID-5 set. Each RAID-5 set is also protected from the failure of a bus by the parity inherent in RAID-5. The RAID-5 sets are striped by a front-end controller connected to the primary local back-end controller, and the striped RAID-5 sets are presented to a host computer as a very large virtual volume. If the individual disks are 9.1 GB in size, the size of the very large virtual volume can reach 500.5 GB.