Chapter 8 Storage

Performance rankings are approximations.

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

 

 

 

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.

8.6.3Storage 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.

170

 

Media Server User’s Guide