ZyXEL NAS326 User Guide - Page 99

Chapter 8 Storage Manager 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 31 JBOD A1 B1 C1 A2 B2 C2 A3 B3 C3 A4 B4 C4 DISK 1 DISK 2 DISK 3 RAID 0 RAID 0 spreads data across two or more disks (data striping) with no mirroring nor parity for data redundancy, so if one disk fails the entire array will be lost. The major benefit of RAID 0 is performance. The following figure shows two disks in a single RAID 0 array. Data can be written and read across disks simultaneously for faster performance. Table 32 RAID 0 A1 A2 A3 A4 A5 A6 A7 A8 DISK 1 DISK 2 RAID 0 capacity is the size of the sum of the capacities of the disks in the RAID 0. For example, if you have four disks of sizes 1 TB, 2 TB, 3 TB and 2 TB respectively in one RAID 0 array, then the maximum capacity is 8 TB. 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. RAID 1 RAID 1 creates an exact copy (or mirror) of a set of data on another disk. This is useful when data backup is more important than data capacity. The following figure shows two disks in a single RAID Cloud Storage User's Guide 99