RAID and Subsystem Architectures Subsystem Architectures
What type of Storage Device? Can we use individual disks for our enterprise storage ?
Does an individual disk offer the features we require; • Resilience • Scalability • Performance
Resilience Individual Drives JBOD
(“Just a Bunch of Disks”)
RAID Array
Data loss if drive fails
Data loss if single drive fails
Protection against failure of an
individual drive Scalability
Limited to individual drive
Limited by maximum no of drives in JBOD
Large Arrays can
scale to many 100’s of drives
Performance
Limited by individual drive
Limited by individual drives
Enhanced by caching & striping
Just a Bunch of Disks (JBOD) storage: JBODs are storage devices in which multiple disks are attached to a common I/O bus and appear as individual attached devices to the network.
JBODs typically do not contain “intelligence.” If RAID is desired, it must be implemented by software.
JBODs frequently use a Fibre Channel Arbitrated Loop as the array backplane to which the disks are connected. Commonly there are two loop ports provided, to allow a secondary loop to be configured, for redundancy. Some FC disks allow both ports to be used at the same time but most allow access through only one port at a time.