Chapter 7 Storage

7.6 Storage Technical Reference

This section provides some background information about the topics covered in this chapter.

7.6.1 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.

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 recreate a volume.

Note: Back up your data before deleting or re-creating a volume!

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 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

 

 

 

7.6.2 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 7.6.3 on page 161 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).

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Media Server User’s Guide