EMC CX500I Configuration Guide - Page 34

RAID Types, RAID 5 Group (Individual Access Array)

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RAID Types and Trade-offs 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. You can choose an additional type of redundant disk - a remote mirror - for any RAID type except a 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, you can create up to 128 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. Figure 2-2 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. 2-4 EMC CLARiiON CX300, CX500, CX500i, and CX700 Storage Systems Configuration Planning Guide

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2-4
EMC CLARiiON CX300, CX500, CX500i, and CX700 Storage Systems Configuration Planning Guide
RAID Types and Trade-offs
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.
You can choose an additional type of redundant disk — a remote
mirror — for any RAID type except a 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,
you can create up to 128 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.
Figure 2-2 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.