Direct Attached Storage (DAS)
Storage devices are attached directly to a single host computer
and use block-level access protocols such as ATA and SCSI.
Physical sharing of the storage devices is not practical and
data sharing must be coordinated through the host computer.
Network Attached Storage (NAS)
Storage devices are attached to multiple hosts through network
interconnects such as Ethernet and use file-level access protocols
such as NFS or C I FS to access data.
Storage Area Networks (SAN)
Storage devices are attached to multiple host computers through network
interconnects and use block-level access protocols such as FC-SCSI and
iSCSI. Physical sharing of storage devices among the host computers is
possible, but the host computers themselves must coordinate data
sharing.
Object-based Storage Devices (OSD)
Storage devices are attached to multiple host computers through a network
interconnect and use an object-level access protocol such as OSD. The
Storage Device itself manages storage resources such as data objects,
space, bandwidth, and connectivity rather than an outside entity.
Intelligent Storage Devices (ISD)
These are storage devices that are aware of the data objects they store.
Given this awareness, ISDs can better manage their own storage resources
(e.g., space, bandwidth, and transaction scheduling) and can also
manipulate their data objects as well as the data inside these objects.
ISDs can be given different capabilities based on how they are to be
used. For example, a medical imaging ISD could know how to manipulate
X-ray images but would not know anything about how to deal with email
files.
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