External Disks; Storage Technical Reference; Volumes And Raid; Table 20 Raid Quick Comparison - ZyXEL Communications NSA-220 PLUS User Manual

5.5.1 External Disks

You may connect USB storage devices that support the following file systems to the NSA.
• Windows File Systems: NTFS, FAT32 and FAT16.
• Linux File Systems: ReiserFS, EXT2, and EXT3.

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.
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
NSA-220 Plus User's Guide
0 1
2 2
S*N S*N/2
100% 50%
None YYYY
Y YYYY
YYYY YYY
YYYY YYY
Chapter 5 Storage
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