Host or Server-side Implimentation in SAN

FC SAN:
* Host or server in SAN architecture consists of HBAs, FC protocol stack, Operating system & Software Applications as shown in the Picture.
* FC Protocol Stack consists of 5 layers (FC0, FC1, FC2, FC3, FC4). each layer corresponds to: physical (FC-0), data link (FC-1, FC-2), network (FC-2, FC-3), and transport (FC-4).
* The SAN storage/disk system is managed by the Host/Server operating system.
Software applications access data via file I/O system calls into the Operating System. The file I/O system calls are handled by the File
System, which manages the directory data structure and mapping from files to disk blocks in an abstract logical disk space.
* The Volume Manager manages the block resources that are located in one or more physical disks in the Disk System and maps the accesses to the logical disk block
space to the physical volume/cylinder/sector address.
* The Fibre Channel protocol stack, ties the Operating System to the Host Bus Adapter(FC HBA) hardware that provides the transport function for block I/O commands to the remote
disk systems across the SAN network.
* The file level I/O initiated by the Software application (SAN management S/W) is mapped into block level I/O by the FC protocol stack & FC interface between the Host/Server and the disk system (Storage Subsystems).
* Fibre Channel is the first network architecture to enable block level storage networking applications.

iSCSI SAN:
* The Host/Server-side implementation is essentially the same as the Fibre Channel SAN. The key difference here is that the Fibre Channel protocol stack & FC Interfaces (FC-HBA, Cables, connectors, Network components) is
replaced by the iSCSI/TCP/IP stack & Ethernet (TCP/IP) Interfaces (iscsi-HBA, Cables, connectors, Network components).
* In FC based SAN, FC protocol stack maps the Block level (I/O) SCSI commands into Fibre Channel Frames & carries SCSI data over FC to remote storage subsystems in SAN envirnoment.
* In iSCSI based SAN, iSCSI/TCP/IP stack maps the Block level (I/O) SCSI commands into TCP/IP Data packets & carries SCSI data over Ethernet to remote storage subsystems in SAN envirnoment.

NOTE: the Picture posted with this topic shows interesting comparison of Host or Server-side Implementation in DAS, SAN (FC & iSCSI) and NAS.