EMC FC5300 User Manual download pdf (Page 34)

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EMC Fibre Channel Storage-System Configuration Planning

RAID Types and Tradeoffs

RAID Types

You can choose from the following RAID types: RAID 5, RAID 3,

RAID 1, RAID 0, RAID 1/0, individual disk unit, and hot spare.

RAID 5 Group (Individual Access Array)

A RAID 5 Group usually consists of five disks (but can have three to

sixteen). A RAID 5 Group uses disk striping. With a RAID 5 Group on

a full-fibre storage system, you can create up to 32 RAID 5 LUNs to

apportion disk space to different users, servers, and applications.

The storage system writes parity information that lets the group

continue operating if a disk fails. When you replace the failed disk,

the SP rebuilds the group using the information stored on the

working disks. Performance is degraded while the SP rebuilds the

group. However, the storage system continues to function and gives

users access to all data, including data stored on the failed disk.

The following figure shows user and parity data with the default

stripe element size of 128 sectors (65,536 bytes) in a five-disk RAID 5

Group. The stripe size comprises all stripe elements. Notice that the

disk block addresses in the stripe proceed sequentially from the first

disk to the second, third, and fourth, then back to the first, and so on.

1 2 ... 29 30 31 32 33 34 35 36 37 38 39 ... 133 134

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EMC FC5300 User Manual Page 34