Jbod; Raid 0; Table 16 Jbod; Table 17 Raid 0 - ZyXEL Communications NSA-220 User Manual

Chapter 6 Storage Screens
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.

6.4.1 JBOD

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 multiple different-sized drives into one
big drive. For example, JBOD could convert 80 GB and 100 GB drives into one large logical
drive of 180 GB. If you have two JBOD volumes (with one disk in each), a failure of one disk
(volume) should not affect the other volume (disk). 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 disks in a single JBOD volume. Data is not written across disks but written
sequentially to each disk until it's full.

Table 16 JBOD

A1
A2
A3
A4
DISK 1

6.4.2 RAID 0

RAID 0 spreads data evenly across two or more disks (data striping) with no mirroring nor
parity for data redundancy, so if one disk fails the entire volume will be lost. The major benefit
of RAID 0 is performance. The following figure shows two disks in a single RAID 0 volume.
Data can be written and read across disks simultaneously for faster performance.

Table 17 RAID 0

A1
A3
A5
A7
DISK 1
66
B1
B2
B3
B4
DISK 2
A2
A4
A6
A8
DISK 2
NSA-220 User's Guide