Today we continue discussing the best practice from storage engineering:
295) A RAID level 4 uses a block inter-leaved parity with a striping unit of a disk block. Block-level striping has the advantage that read requests the size of a disk block can be served entirely by the disk where the requested block resides. The write of a single block still requires a read-modify-write cycle, but only one data disk and the check disk are involved and the difference between the old data block and the new data block is noted
296)
A RAID level 5 uses a block inter-leaved distributed parity. The parity blocks are distributed uniformly over all disks, instead of sorting them on a single check disk. This has two advantages. First, several write requests potentially be processed in parallel, since the bottleneck of a unique check is removed. Second, read requests have a higher degree of parallelism. This level usually has the best performance.
297) A RAID level 6 uses P+Q redundancy. Recovery from the failure of a single disk is usually not sufficient in very large disk arrays. First, a second disk might fail before replacement and second the probability of a second disk failing is not negligible. A RAID level 6 system uses Reed-Solomon codes to be able to recover from two simultaneous disk failures.
298) A RAID level 10+0 is a stripe of RAID1+0. In this array of RAID1+0, the RAID0 is implemented in software while RAID1+0 is implemented in hardware.
299) A RAID1+0, RAID3+0, RAID5+0, RAID6+0 and RAID10+0 are referred to as nested RAIDs and hybrid RAIDs and their usage diminishes with the growing and now established popularity of Network Attached Storage and cluster based partitioned approach. Blade servers with consolidated storage and centralized management have facilitated cutting VM slices.
300) Disks compete not only with other disks but also with other forms of storage such as Solid-State Drives.
295) A RAID level 4 uses a block inter-leaved parity with a striping unit of a disk block. Block-level striping has the advantage that read requests the size of a disk block can be served entirely by the disk where the requested block resides. The write of a single block still requires a read-modify-write cycle, but only one data disk and the check disk are involved and the difference between the old data block and the new data block is noted
296)
A RAID level 5 uses a block inter-leaved distributed parity. The parity blocks are distributed uniformly over all disks, instead of sorting them on a single check disk. This has two advantages. First, several write requests potentially be processed in parallel, since the bottleneck of a unique check is removed. Second, read requests have a higher degree of parallelism. This level usually has the best performance.
297) A RAID level 6 uses P+Q redundancy. Recovery from the failure of a single disk is usually not sufficient in very large disk arrays. First, a second disk might fail before replacement and second the probability of a second disk failing is not negligible. A RAID level 6 system uses Reed-Solomon codes to be able to recover from two simultaneous disk failures.
298) A RAID level 10+0 is a stripe of RAID1+0. In this array of RAID1+0, the RAID0 is implemented in software while RAID1+0 is implemented in hardware.
299) A RAID1+0, RAID3+0, RAID5+0, RAID6+0 and RAID10+0 are referred to as nested RAIDs and hybrid RAIDs and their usage diminishes with the growing and now established popularity of Network Attached Storage and cluster based partitioned approach. Blade servers with consolidated storage and centralized management have facilitated cutting VM slices.
300) Disks compete not only with other disks but also with other forms of storage such as Solid-State Drives.
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