Patent ID: 7669076

Claim:
A system for estimating the availability of data, the system comprising: a set of disks comprising a plurality of hard disks; a processor in communication with each of the plurality of hard disks; and a computer readable medium in communication with the processor, the computer comprising a set of instructions executable by the processor, the set of instructions comprising: instructions to identify a set of operating characteristics for each of the plurality of hard disks; instructions to calculate, based at least in part on the operating characteristics of the plurality of hard disks, a first estimated mean time to data loss for the set of disks, the first estimated mean time to data loss corresponding to a first configuration of the set of disks, wherein the first configuration is a triple-mirroring configuration, in which a data block on a first hard disk is mirrored on each of two other hard disks, and wherein a first value represents the first estimated mean time to data loss, the first value being calculated using a formula of E ⁡ ( t 0 ) ≈ μ 1 ⁢ μ 2 2 ⁢ nk ⁡ ( k - 1 ) ⁢ λ 3 in which E(t 0 ) is the first value, μ 1 is a first rebalance rate signifying a rate at which data from a first disk can be restored to another disk, μ 2 is a second rebalance rate signifying a rate at which data from a second disk can be restored to another disk, wherein the second disk is a partner of the first disk, k represents a number of disk partners for the first disk, and λ is the failure rate of a disk, expressed as a reciprocal of a mean time to failure for a disk; instructions to calculate, based at least in part on the operating characteristics of the plurality of hard disks, a second estimated mean time to data loss for the set of disks, the second estimated mean time to data loss corresponding to a second configuration of the set of disks; instructions to select, from among at least the first configuration and the second configuration, a configuration with the greatest estimated mean time to data loss; and instructions to configure, according to the selected configuration, a disk group from the set of disks.