Abstract: The present invention relates to a method for testing the operability of a Peer to Peer Remote Copy (PPRC) data storage system in disaster situations. A PPRC data storage system includes a host processor, a primary storage subsystem and a secondary storage subsystem where the secondary storage subsystem is coupled to the primary storage subsystem for mirroring of data therebetween. A command is sent from the host processor directing the primary storage subsystem to simulate a disaster. Upon detection of the disaster, the host establishes direct communication with the secondary storage subsystem, and validates the integrity of the system by comparing data from the secondary storage subsystem to data from the primary storage subsystem.

Abstract: A data storage system including first, second, third and fourth virtual storage volumes, the first and second virtual storage volumes controlled to enable a mirroring and synchronization of data therebetween. The data storage system further includes a first processor that is responsive to a “copy pair” command or its equivalent to copy a directory from the first virtual storage volume to a directory of the third virtual storage volume. The first processor also dispatches a copy command, or its equivalent, to copy the directory of the second virtual storage volume to the directory of the fourth storage volume. A second processor is responsive to the copy command to cause a copying of the directory of the second virtual storage volume to the directory of the fourth virtual storage volume. Thus, the third and fourth virtual storage volumes are controlled to include directories which duplicate directories of the first and second virtual storage volumes.

Abstract: A data storage system includes at least first, second and third virtual storage volumes, the second and third virtual storage volumes being remotely coupled as a PPRC pair to enable a mirroring of data therebetween. The storage system is responsive to a snapshot command from a host processor, to cause transfer of the directory of the first virtual storage volume to the second virtual storage volume. The storage system then invokes a PPRC mirroring procedure which (i) detects an unsynchronized condition between the second and third virtual storage volumes (upon transfer of the directory from the first virtual storage volume to the second virtual storage volume), and (ii) causes a transfer of data, pointed to by the transferred directory, to the third virtual storage volume, until the second and third virtual storage volumes are again in synchronism.

Abstract: The present invention provides a method and apparatus for setting up a Peer-to-Peer Remote Copy (PPRC) session and snapshot copying a remote secondary volume to another volume on the remote subsystem. The apparatus includes a primary storage subsystem having a primary data-storage device with at least a primary volume. A primary processing unit relays a request to perform a snapshot copy of at least a portion of the primary volume to a secondary storage subsystem. The secondary storage subsystem includes a secondary data-storage device having a secondary volume which is maintained in a duplexed state with the primary volume through the use of remote copy sessions. A secondary processing unit, responsive to the relayed request can perform an equivalent of a snapshot copy of at least a portion of the primary volume by making a snapshot copy of a corresponding portion of the secondary volume.

Abstract: A method and system for the automatic data recovery for a duplex pair is provided. The preferred embodiment includes the discovery of lost data on the first subsystem. A copy of the lost data is automatically transferred from the second subsystem to the first subsystem. Then the copy of the lost data is automatically written into the first subsystem. The host processor and the operator is unaware data had been lost. The method and system of the present invention eliminates the need to terminate the job which triggered the discovery of the lost data. It also eliminates the need for any involvement of the operator in the data recovery process.

Abstract: Copies of data that are stored on tracks of a primary disk volume and a backup disk volume are synchronized by a method which reduces the amount of data that is transferred. The primary disk volume includes tracks with current data (i.e., non-empty tracks) and tracks with no current data (i.e., empty tracks). The method transfers to the backup disk volume only data from non-empty tracks on the primary disk volume and then writes the data onto tracks in the backup disk volume that correspond to the non-empty tracks of the primary disk volume. Prior to writing of the data onto the backup disk volume, it is preferred that the backup disk volume have all tracks erased so that after the write action, only the tracks with current data have data written therein. Further, at the primary disk volume, only tracks having current data are read. Accordingly, substantial savings in processing and data transfer times are achieved.

Abstract: A system incorporating the invention stores data on communicating disk drives in such a manner as to enable recovery of the data in the event a failure of one of the disk drives. The system includes a first disk drive and a second disk drive, both for storing compressed data records in compressed track formats. Each compressed data record includes a CRC value. A cache stores compressed tracks of data records that are read from the first disk drive and a CRC value is calculated for each stored track of compressed data records. That CRC value is appended to the compressed track. A switch is coupled between the cache, a host processor and the second disk drive for dispatching and receiving tracks of compressed data records between the first disk drive and the second disk drive.