RE: question about drives configuration
- From: uttamkp@xxxxxxxxxxxxxxxxxxxx (Uttam Parui[MS])
- Date: Thu, 07 Jul 2005 20:12:37 GMT
Because many vendors confuse the terms RAID 10, RAID 1+0, and RAID 0+1, use the terms mirrored striping and striped mirroring.
Striped mirroring is the best solution for a database server requiring high performance and high availability. Capacity can be a problem, however, because of the number of disks required and their cost.
More Info:
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Striped Mirroring
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Striped mirroring writes logical blocks of data across two or more mirrored sets of disks, creating a single volume with no redundant information between the mirrored sets of disks. Each mirrored set of disks consists
of two or more disks. Striped mirroring provides the same high level of availability as mirroring. The available capacity of a striped mirror is equal to that of each disk in the mirror set (in a two-disk mirror set, 50
percent of the disk capacity is used for data protection). Unlike mirroring, however, striped mirroring provides symmetrical performance. Read performance is very fast because data is available from each disk in
the mirror. In striped mirror implementation, RAID array and SAN controllers support simultaneous reads from each member of the mirror, which maximizes read performance. Write performance is also fast because
writes occur simultaneously across each mirrored set.
With striped mirroring, if a drive fails, read and write performance is slightly reduced, but only for data stored on the mirror set containing the failed disks. Read and write performance to and from the other mirrored
sets is not affected. Striped mirroring can survive the failure of multiple drives, provided at least one drive in each mirrored set survives.
Mirrored Striping
===============
Mirrored striping writes logical blocks of data across two or more disks, creating a single logical volume with no redundant information between the disks, and then mirrors the volume. Read and write performance is
very fast, but mirrored striping is not as fault tolerant as striped mirroring. When a single disk in a stripe fails, the data remains available in the other stripe, but the stripe is broken. With one broken stripe, the failure of a
disk in the remaining stripe causes the data to become unavailable. In addition, when a stripe fails, read performance is slower because only one stripe is functional.
Best Regards,
Uttam Parui
Microsoft Corporation
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