Abstract: Synchronous mirroring of data stored in a first storage system is performed by storing a mirror copy of the data at a remote second storage system. A first snapshot of the data stored in the first storage system is created, and a second snapshot of the mirror copy in the second storage system is created. A first signature of the first snapshot and a second signature of the second snapshot are calculated, and the first and second signatures are compared to verify whether or not the data in the first storage system is identical to the mirror copy in the second storage system.

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.