US 6,636,984 B1 · System and method for recovering data from mirror drives following system crash

Abstract

A system and method for recovering data from parallel mirror drives following a system crash. During a parallel write to a mirrored disk array, it is unknown which of the disks comprising the disk array write the data to disk first. A completion array is used to record the first disk that stores a data item at a given address. During recovery from a system failure, the completion array is read to identify the last writes performed before the system failure occurred. The disk identified in the completion array is used as the master disk for the particular address identified. Data is read from that disk and address and propagated to the other disks in the mirrored disk array. Other items in the completion array may identify different disks to be used as the master for other addresses. In one embodiment, the completion array is stored in a reserved area of memory that is dumped to disk during a system failure and restored from disk during a subsequent system recovery. In one embodiment, a mirror write consistency check (MWCC) is used in conjunction with the completion array to record writes that are about to occur to the drive array as well as the first drive to successfully store the data. A computer system and a computer program product for recovering from system, failure using a parallel mirror drive array are further disclosed.

Claims22

Dependent claims

A computer system comprising:

a computer including:
one or more processors;
a memory accessible by the one or more processors;
a plurality of disks accessible by the one or more processors, each of the plurality of disks including a disk identifier and each of the plurality of disks including a plurality of disk addresses;
one or more data units, each data unit stored at a disk address from the plurality of disk addresses;
one or more first disk identifiers, each of the first disk identifiers corresponding to the first of the plurality of disks to store the corresponding data units;
a memory area within the memory, the memory area including the stored disk addresses and the corresponding first disk identifiers;
a recovery tool for recovering the plurality of disks from a computer system failure, the recovery tool including:
means for locating the memory area;
means for reading the disk addresses and the corresponding first disk identifiers from the memory area;
means for reading the data stored at the corresponding unique disk addresses from the disks of the plurality of disks corresponding to the first disk identifiers;
and
means for writing the data to the other disks of the plurality of disks.

10 more elements

Dependencies are inferred from the claim text.

System and method for recovering data from mirror drives following system crash

Life of this patent

System and method for recovering data from mirror drives following system crash

Life of this patent

Abstract

Claims22