McDATA 3000 manual FC/SCSI Tape Pipelining, Buffering, Emulation, and Data Protection

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FC/SCSI Tape Pipelining

This chapter provides an overview on FC/SCSI Tape Pipelining (Device Extension), LUN discovery, and dynamic and static mapping.

FC/SCSI Tape Pipelining on the UltraNet Edge 3000 allows tape backup performance over distances up to thousands of miles. It performs over long distances without the distance performance penalty found in non-pipelined operations.

Buffering, Emulation, and Data Protection

FC/SCSI Tape Pipelining uses device emulation as the means to extend the devices from one end of the network to the other. The following sections discuss how buffering, emulation and error recovery work.

Buffering and	Before addressing the impact of device emulation on tape backup, it
Emulation	is helpful to understand how buffered devices operate when natively
	attached to a server.
	The concept of buffering was developed primarily to increase
	performance between a server and a device’s control unit.
	Upon receiving a command from the server, non-buffered devices
	need to complete the command in its entirety prior to acknowledging
	completion to the server. While this synchronous method of data
	transfer is very safe from a command completion perspective, it
	creates I/O performance issues for the server by tightly coupling each
	command completion to overall completion of the host I/O transfer.

FC/SCSI Tape Pipelining

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