Jbod; Raid 0; Table 20 Jbod; Table 21 Raid 0 - ZyXEL Communications NSA-220 User Manual

Chapter 6 Storage Screens

6.9.1 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 20 JBOD

A1
A2
A3
A4
DISK 1

6.9.2 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 21 RAID 0

A1
A3
A5
A7
DISK 1
RAID 0 capacity is the size of the smallest disk multiplied by the number of disks you have
configured at RAID 0 on the NSA. For example, if you have two disks of sizes 100 GB and
200 GB respectively in a RAID 0 volume, then the maximum capacity is 200 GB (2 * 100 GB,
the smallest disk size) and the remaining space (100 GB) is unused.
Typical applications for RAID 0 are non-critical data (or data that changes infrequently and is
backed up regularly) requiring high write speed such as audio, video, graphics, games and so
on.
82
B1
B2
B3
B4
DISK 2
A2
A4
A6
A8
DISK 2
NSA-220 User's Guide