Choosing A Storage Method For A Volume; Table 15 Raid Quick Comparison - ZyXEL Communications NSA-220 User Manual

Back up your data before deleting or re-creating a volume!
For example if you originally have one disk configured at 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 15 RAID Quick Comparison

RAID Level
Number of Disks
Capacity
Storage Efficiency
Fault Tolerance
Availability
Read Performance
Write Performance

6.3.1 Choosing A Storage Method For a Volume

The following is a guide to help you choose a storage method for the various number of disks
supported on the NSA. See
the RAID levels used on the NSA. Typical applications for each method are also shown there.
6.3.1.1 One Disk
If you only have one disk, you must use JBOD. All disk space is used for your data - none is
used for backup. If the disk fails, then you lose all the data on that volume (disk).
6.3.1.2 Two Disks:
You may choose JBOD, RAID 0 or RAID 1. With two disks you could create:
• up to two JBOD volumes
• one RAID 0 or RAID 1 volume
• Choose JBOD for flexibility and maximum usage of disk space for data. You can
either add an additional disk to your one-disk JBOD volume (and you don't have to
re-create shares, access rights etc.) or create a different JBOD volume (and create new
shares, access rights and so on).
NSA-220 User's Guide
0 1
2 2
S*N S*N/2
100% 50%
None YYYY
Y YYYY
YYYY YYY
YYYY YYY
Section 6.4 on page 65
Chapter 6 Storage Screens
for theoretical background on JBOD and
63