Adaptec 2820SA User Guide - Page 72

RAID 50 Arrays

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Appendix B: Understanding RAID ● 72 RAID 50 Arrays A RAID 50 array is built from six to forty-eight disk drives configured as two or more RAID 5 arrays, and stripes stored data and parity data across all disk drives in both RAID 5 arrays. (For more information, see RAID 5 Arrays on page 70.) Note: Because the Adaptec 2420SA RAID controller doesn't support more than four disk drives, it doesn't support RAID 50 arrays. The parity data provides data protection, and striping improves performance. RAID 50 arrays also provide high data transfer speeds. Drive segment size is limited to the size of the smallest disk drive in the array. For example, three 250 GB disk drives and three 400 GB disk drives comprise two equal-sized RAID 5 arrays with 500 GB of stored data and 250 GB of parity data. The RAID 50 array can therefore contain 1000 GB (2 x 500 GB) of stored data and 500 GB of parity data. RAID 50 Logical Drive = 1000 GB plus Parity RAID 5 A Each RAID 5 Logical Drive has 500 GB Data Storage 250 GB Parity Data RAID 5 B 1, 5, P 3, P, 9 P, 7, 11 Drive 1 250 GB Drive 2 250 GB Drive 3 250 GB 2, 6, P 4, P, 10 P, 8, 12 Total Unused Space = 150 GB Drive 4 400 GB Drive 5 400 GB Drive 6 400 GB In the example above, P represents the distributed parity data.

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Appendix B: Understanding RAID
●
72
RAID 50 Arrays
A RAID 50 array is built from six to forty-eight disk drives configured as two or more RAID 5
arrays, and stripes stored data and parity data across all disk drives in both RAID 5 arrays. (For
more information, see
RAID 5 Arrays
on page 70
.)
Note:
Because the Adaptec 2420SA RAID controller doesn’t support more than four disk
drives, it doesn’t support RAID 50 arrays.
The parity data provides data protection, and striping improves performance. RAID 50 arrays
also provide high data transfer speeds.
Drive segment size is limited to the size of the smallest disk drive in the array. For example,
three 250 GB disk drives and three 400 GB disk drives comprise two equal-sized RAID 5 arrays
with 500 GB of stored data and 250 GB of parity data. The RAID 50 array can therefore contain
1000 GB (2 x 500 GB) of stored data and 500 GB of parity data.
In the example above, P represents the distributed parity data.
RAID 5
B
RAID 50
Logical Drive
=
1000 GB
plus Parity
RAID 5
A
Each RAID 5 Logical Drive has
500 GB Data Storage
250 GB Parity Data
Drive 1
250 GB
Drive 2
250 GB
Drive 3
250 GB
Drive 4
400 GB
Drive 5
400 GB
Drive 6
400 GB
1, 5, P
3, P
, 9
P
, 7, 11
2, 6, P
4, P
, 10
P
, 8, 12
Total Unused
Space = 150 GB