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IBM Power Systems 775 for AIX and Linux HPC Solution
Arbitrarily sized disk arrays: The number of disks is not restricted to a multiple of the RAID
redundancy code width, which allows flexibility in the number of disks in the RAID array.
Multiple redundancy schemes: One disk array supports VDisks with different redundancy
schemes; for example, Reed-Solomon and replication codes.
Disk hospital: A disk hospital asynchronously diagnoses faulty disks and paths, and
requests replacement of disks by using past health records.
Automatic recovery: Seamlessly and automatically recovers from primary server failure.
Disk scrubbing: A disk scrubber automatically detects and repairs latent sector errors in
the background.
Familiar interface: Standard GPFS command syntax is used for all configuration
commands, including, maintaining, and replacing failed disks.
Flexible hardware configuration: Support of JBOD enclosures with multiple disks
physically mounted together on removable carriers.
Configuration and data logging: Internal configuration and small-write data are
automatically logged to solid-state disks for improved performance.
GPFS Native RAID features
This section describes three key features of GPFS Native RAID and how the functions work:
data redundancy that use RAID codes, end-to-end checksums, and declustering.
RAID codes
GPFS Native RAID automatically corrects for disk failures and other storage faults by
reconstructing the unreadable data by using the available data redundancy of either a
Reed-Solomon code or N-way replication. GPFS Native RAID uses the reconstructed data to
fulfill client operations, and in the case of disk failure, to rebuild the data onto spare space.
GPFS Native RAID supports two- and three-fault tolerant Reed-Solomon codes and
three-way and four-way replication, which detect and correct up to two or three concurrent
faults1. The redundancy code layouts that are supported by GPFS Native RAID, called
tracks
,
are shown in Figure 1-57.
Figure 1-57 Redundancy codes that are supported by GPFS Native RAID
GPFS Native RAID supports two- and three-fault tolerant Reed-Solomon codes, which
partition a GPFS block into eight data strips and two or three parity strips. The N-way
replication codes duplicate the GPFS block on N - 1 replica strips.
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