ZyXEL Communications NSA320, User Manual

Page: 170 / 384

Chapter 8 Storage
Media Server User’s Guide
170
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
Section 8.6.3 on page 170 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
to your one-disk JBOD volume later without having to re-create shares, access rights, and so on.
Alternatively, you could create a different JBOD volume if you install a second disk. (and create new
shares, access rights and so on).
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.
• If you have a 2-bay model, you can choose RAID 0 if performance matters more than data
security. RAID 0 has the fastest read and write performance but if one disk fails you lose all
your data on the volume. It has fast performance as it can read and write to two disks
simultaneously. Performance may matter more than data security to gamers for example. This
method may also be acceptable for data that is already backed up somewhere else.
• Choose RAID 1 if data security is more important than performance. Since RAID 1 mirrors data
onto a second disk, you can recover all data even if one disk fails, but the performance is slower
than RAID 0.
8.6.3 Storage Methods
This section contains theoretical background on JBOD and the RAID levels used on the NSA.
Redundant Array of Independent Disks (RAID) is a method of storing data on multiple disks to
provide a combination of greater capacity, reliability, and/or speed. JBOD (Just a Bunch Of Disks) is
not a RAID storage method but it is included in this discussion.
Table 27
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