3Ware 9550SXU-12 User Manual page 23

Understanding RAID Concepts and Levels
Figure 7. RAID 50 Configuration Example
Single Disk
A single drive can be configured as a unit through 3ware software. (3BM,
3DM 2, or CLI). Like disks in other RAID configurations, single disks
contain 3ware Disk Control Block (DCB) information and are seen by the OS
as available units.
Single drives are not fault tolerant and therefore not recommended for high
availability systems unless additional precautions are taken to prevent system
hangs and data loss.
JBOD
A JBOD (acronym for "Just a Bunch of Disks") is an unconfigured disk
attached to your 3ware RAID controller. JBOD configuration is no longer
supported in the 3ware 9000 series. AMCC recommends that you use Single
Disk as a replacement for JBOD, to take advantage of advanced features such
as caching, OCE, and RLM.
JBOD units are not fault tolerant and therefore not recommended for high
availability systems unless additional precautions are taken to prevent system
hangs and data loss.
Hot Spare
A hot spare is a single drive, available online, so that a redundant unit can be
automatically rebuilt in case of drive failure.
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