Chapter 5 Storage Manager
NAS Series User’s Guide
98
RAID 0 capacity is the size of the sum of the capacities of the disks in the RAID 0. For example, if you
have four disks of sizes 1 TB, 2 TB, 3 TB and 2 TB respectively in one RAID 0 array, then the maximum
capacity is 8 TB.
Typical applications for RAID 0 are non-critical data (or data that changes infrequently and is backed
up regularly) requiring high write speed such as audio, video, graphics, games and so on.
RAID 1
RAID 1 creates an exact copy (or mirror) of a set of data on another disk. This is useful when data
backup is more important than data capacity. The following figure shows two disks in a single RAID 1
array with mirrored data. Data is duplicated across two disks, so if one disk fails, there is still a copy of the
data.
As RAID 1 uses mirroring and duplexing, a RAID 1 array needs an even number of disks (two or four for
the NAS).
RAID 1 capacity is limited to the size of the smallest disk in the RAID array. For example, if you have two
disks of sizes 150 GB and 200 GB respectively in one RAID 1 array, then the maximum capacity is 150 GB
and the remaining space (50 GB) is unused.
Typical applications for RAID 1 are those requiring high fault tolerance without need of large amounts of
storage capacity or top performance, for example, accounting and financial data, small database
systems, and enterprise servers.
RAID 6
RAID 6 can tolerate two simultaneous drive failures by calculating dual distributed parity data on striped
data across disks. Dual parity provides extra data protection, however, it is slower to write than most
other RAID levels.
RAID 6 uses parity to store redundant data on space equal to the size of two disks for later data
recovery. Therefore, on a RAID 6 array, only 50% of the space is available as usable capacity. If you
have four disks of sizes 1TB, 1TB, 2TB, 2TB respectively in one RAID 6 array, then the maximum capacity of
Table 51 RAID 1
A1 A1
A2 A2
A3 A3
A4 A4
DISK 1 DISK 2
To Next Page
Loading...
