ZyXEL NSA325 User Manual
Chapter 8 Storage
Media Server User’s Guide
166
8.6 Storage Technical Reference
This section provides some background information about the topics covered in this chapter.
8.6.1 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.
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.
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.
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.
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.
8.6.2 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
supported on the NSA. See
for theoretical background on JBOD and the
RAID levels used on the NSA. Typical applications for each method are also shown there.
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). You can add another disk
backup. If the disk fails, then you lose all the data on that volume (disk). You can add another disk
Table 24
RAID Quick Comparison
RAID Level
0
1
Number of Disks
2
2
Capacity
S*N
S*N/2
Storage Efficiency
100%
50%
Fault Tolerance
None
YYYY
Availability
Y
YYYY
Read Performance
YYYY
YYY
Write Performance
YYYY
YYY