ZyXEL Communications NSA-2401 User Manual

Chapter 6 Storage Screens

NSA-2401 User’s Guide

lost. Parity protection is used with striping, and the “n” pieces of data are typically the 
blocks or bytes distributed across the drives in the array. The parity information can either 
be stored on a separate, dedicated drive, or be mixed with the data across all the drives in 
the array.

"

In the following figures, A1, A2, A3 and so on are blocks of data from the A file. 
Similarly, B1, B2, B3 and C1, C2, C3 ar blocks of data from the B and C files.

• Minimum number of disks: 1

• Total capacity: Sum of the member disks

• Advantages: Maximum storage capacity, especially for disks of mixed sizes. Flexibility 

(you can add disks to the JBOD 

• Disadvantages: Not as fast or reliable as RAID.

JBOD allows you to combine multiple physical disk drives into a single virtual one, so they 
appear as a single large disk. JBOD can be used to turn several different-sized drives into one 
big drive. For example, JBOD could convert 100 GB, 200 GB, 250 GB, and 500 GB drives 
into one large logical drive of 1050 GB. Since data isn’t striped across disks, if one disk fails, 
you should just lose the data on that disk (but you may lose data in the whole array depending 
on the nature of the disk failure). You can add disks to the JBOD array later (using the Add 
disk to JBOD feature) and even remove them so JBOD offers a lot of flexibility. However 
JBOD read performance is not as good as RAID as only one disk can be read at a time and 
they must be read sequentially.

 

The following figure shows three disks in a single JBOD array. 

Data is not written across disks but written sequentially to each disk until it’s full.

 

Table 37   JBOD