Storage Technical Reference; Volumes And Raid - ZyXEL Communications NSA-220 Plus User Manual

Chapter 5 Storage

5.6 Storage Technical Reference

This section provides some background information about the topics covered in
this chapter.

5.6.1 Volumes and RAID

A volume is a storage area on a disk or disks. You can create volumes on the
internal disks and external disks attached to the USB port(s). You can spread a
volume across internal disks but not between internal and external disks.
RAID (Redundant Array of Independent Disks) or JBOD is the storage method that
the NSA uses. The storage method you use depends on how many disks you have
and how many volumes you want to create. It's important that you consider this
carefully as all data is deleted when you re-create a volume.
Note: Back up your data before deleting or re-creating a volume!
For example if you originally have one disk configured as JBOD, and you then
install another disk and want to configure the two disks to use RAID 1, you should
first back up all your data on the two disks (see the Memeo Autobackup utility on
the included CD) and then restore your data later after you create the new volume
type.
Below is a table that summarizes some attributes of the various RAID levels as
supported on the NSA. For capacity and storage efficiency, "S" is the size of the
smallest drive in the array, and "N" is the number of drives in the array.
Storage efficiency assumes all drives are of identical size.
Performance rankings are approximations.
Table 20 RAID Quick Comparison
RAID Level
Number of Disks
Capacity
Storage
Efficiency
Fault Tolerance
Availability
Read
Performance
Write
Performance
120
0 1
2 2
S*N S*N/2
100% 50%
None YYYY
Y YYYY
YYYY YYY
YYYY YYY
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