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NSA-2400 User’s Guide

Chapter 6 Storage 82

6.3.1.1 RAID 0

Level 0 is a striped disk array without fault tolerance. It provides data striping (spreading out

blocks of each file across multiple disk drives) but no redundancy so if one disk fails the entire

volume will be lost. The major benefit of RAID 0 is performance.

RAID level 0 can be configured with one or more disks, and its capacity is the size of the

smallest disk multiplied by the number of disks you have configured at RAID 0 on the NSA.

For example, if you have four disks of sizes 100 GB, 150 GB, 150 GB and 200 GB

respectively in one RAID 0 volume, then the maximum capacity is 400 GB (4 * 100 GB, the

smallest disk size) and the remaining space (300 GB) is unused.

Note: If one disk fails then all data in the volume is lost.

Note: RAID 0 was not available on the NSA at the time of writing. When it is available,

you must use a disk 1-2 pair and/or a disk 3-4 pair; you cannot have four

volumes at RAID 0.

6.3.1.2 RAID 1

RAID 1 uses mirroring and duplexing, so a RAID 1 volume needs an even number of disks

(two or four for the NSA). All disk(s) (other than the first) are an exact mirror of the first. A

two-disk RAID 1 volume can survive a one-disk failure and continue running. If a disk fails,

the data is retrieved from the surviving disk.

Note: RAID 1 on the NSA supports a disk 1-2 pair and/or a disk 3-4 pair

RAID 1 capacity is limited to the size of the smallest disk in the RAID set. For example, if you

have two disks of sizes 150 GB and 200 GB respectively in one RAID 1 volume, then the

maximum capacity is 150 GB and the remaining space (200 GB) is unused.

6.3.1.3 RAID 5

RAID 5 provides the best balance of capacity and performance while providing data

redundancy. It provides redundancy by striping data across three or more disks and keeping

the parity information on one of the disks in each stripe. In case of disk failure, the surviving

disks and the parity disk are used to reconstruct the lost data, providing that data transparently

to the user application. When you replace the failed disk with a good disk, the reconstructed

data is written out to the new disk, and when the resynchronization process is complete, the

volume returns to its original state.

Note: You need four hard disks to use RAID 5 on the NSA.

The capacity of a RAID 5 volume is the smallest disk in the RAID set multiplied by one less

than the number of disks in the RAID set. For example, if you have four disks of sizes 150 GB,

150 GB, 200 GB and 250 GB respectively in one RAID 5 volume, then the maximum capacity

is 450 GB (3 * 150 GB, the smallest disk size) and the remaining space (300 GB) is unused.

1. Not available at the time of writing.

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ZyXEL Communications NSA-2400 Betriebsanweisung Seite 82