Chapter 5 Storage Manager
NAS Series User’s Guide
99
the array is the capacity of the smallest drive (1TB, 1TB, 2TB, 2TB) * (Number of disks - 2) = 1TB * (4-2) = 2TB.
The remaining space (2 TB) is unused.
RAID 10
RAID 10 (RAID 1+0) is a nested RAID where two RAID 1 arrays are stored on the physical disks with a RAID
0 array on top. It is a stripe of mirrors. RAID 1 provides redundancy while RAID 0 boosts performance. The
following figure shows two disks in two RAID 1 arrays. Data is duplicated across two disks, so if one disk
fails, there is still a copy of the data. These two arrays are configured as a single RAID 0 array for faster
performance
.
Typical applications for RAID 10 are those requiring both high performance and reliability such as
enterprise servers and high-end moderate-sized database systems. RAID 10 is often used in place of
RAID 1 or RAID 5 by those requiring higher performance. It may be used instead of RAID 1 for
applications requiring more capacity.
RAID 5
RAID 5 provides the best balance of capacity and performance while providing data redundancy. It
provides redundancy by striping data across three disks and keeps the parity information (AP) on the
fourth disk (in each stripe). In case of disk failure, data can be recovered from the surviving disks using
the parity information. When you replace the failed disk, the reconstructed data is written onto the new
disk. Re-synchronize the array to have it return to its original state. The following example shows data
Table 52 RAID 6
RAID 6
A1 A2 AP AQ
B1 BP BQ B2
CP CQ C1 C2
DQ D1 D2 DP
DISK 1 DISK 2 DISK 3 DISK 4
Table 53 RAID 10
RAID 0
RAID 1 RAID 1
A1 A1 A2 A2
A3 A3 A4 A4
A5 A5 A6 A6
A7 A7 A8 A8
DISK 1 DISK 2 DISK 3 DISK 4
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