RAID 4: Block-level striping with dedicated parity.
Each block is written onto a data disk. Parity for each blocks is generated during writes and recorded on the parity disk and checked on reads.
Capacity: (Size of smallest
disk) * (Number of disks - 1)
Advantages:
Read Performance is very good.(Better than
Raid 5)
Fault tolerant, can loose one or more disks with little to no impact.
Disadvantages:
Expensive controller needed to support RAID 4.
Write performance is fair.
Long rebuild times on failed disks.
RAID 4 is not as commonly used as
RAID 3 and
RAID 5, because it is a comprimise between the two that doesn't have a well-defined target market.
Network Appliance
{www.networkappliance.com), a creator of
CIFS/
NFS capable network atached storage
NAS solutions is a primary user of RAID 4.
Network Appliance is also known for their Write Anywhere File Layout
WAFL®.