ZyXEL Communications NSA-220 ユーザーズマニュアル

 Chapter 6 Storage Screens

NSA-220 User’s Guide

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 volume 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 volume needs an even number of disks 
(two or four for the NSA).

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 volume, 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.

If a hard disk fails and you’re using a RAID 1 volume, then your data will still be available 
(but at degraded speeds until you replace the hard disk that failed and resynchronize the 
volume). However, RAID cannot protect against file corruption, virus attacks, files incorrectly 
deleted or modified, or the NSA malfunctioning. Here are some suggestions for helping to 
protect your data.

• Place the NSA behind a hardware-based firewall. It should have stateful packet inspection, 

IDP (Intrusion Detection and Prevention), and anti-virus (like ZyXEL’s ZyWALL UTM 
products for example).

• Use anti-virus software on your computer to scan files from others before saving the files 

on the NSA.

• Keep another copy of important files (preferably in another location).

Table 22   RAID 1