2
RAID Types
2-9
RAID Types and Tradeoffs
Figure 2-5 RAID 1/0 Group
A RAID 1/0 Group can survive the failure of multiple disks,
providing that one disk in each image pair survives.
Individual Disk Unit An individual disk unit is a disk bound to be independent of any
other disk in the cabinet. An individual unit has no inherent high
availability, but you can make it highly available by using software
mirroring with another individual unit. You can create one LUN per
individual di sk unit. If you want to a pportion the disk space, you can
do so using partitions, file systems, or user directories.
Hot Spare A hot spare is a dedicated replacement disk on which users cannot
store information. A hot spare is global: if any disk in a RAID 5
Group, RAID3 Group, RAID 1 mirrored pair, or RAID 1/0 Group
fails, the SP automatically rebuilds the failed disk’s structure on the
hot spare. When the SP finishes rebuilding, the disk group functions
EMC1818
Stripe
element
size
Stripe
size …
…
…
…
…
User data
First disk of primary image
Second disk of primary image
Third disk of primary image
Third disk of secondary image
First disk of secondary image
Second disk of secondary image
512-639128-255 1664-17911280-1407896-1023
1536-16631152-1279768-895
…
512-639
1024-1151
1024-1151
1536-16630-127
128-255
640-767
640-767
1152-1279
256-383
256-383
768-895
1664-1791
384-511
1280-1407
1792-1919
1792-1919
896-1023
1408-1535
1408-1535
Stripe
Blocks
0-127 384-511