HP AA979A - StorageWorks SAN Switch 2/8V Administrator's Manual page 381

Fastwrite and tape pipelining
When the FCIP link is the slowest part of the network and it affects speed, consider using fastwrite and
tape write acceleration, called "tape pipelining." Supported only in Fabric OS 5.2.x and higher, fastwrite
and tape pipelining are two features that provide accelerated speeds to FCIP tunnels in some
configurations:
• Fastwrite accelerates the SCSI write I/Os over FCIP.
• Tape pipelining accelerates SCSI write I/Os to sequential devices (such as tape drives) over FCIP, which
reduces the number of round-trip times needed to complete the I/O over the IP network and speeds up
the process. In order to use tape pipelining, you must enable fastwrite as well.
• Both sides of an FCIP tunnel must have matching configurations for these features to work.
Unlike IPSec, compression, fastwrite, and tape pipelining features do not require any predefined
configurations. This makes it possible to enable these features by adding optional parameters such as
–c, -f, or -t when you create FCIP tunnels.
Enabling fastwrite and tape pipelining
Fastwrite and tape pipelining require no parameters. Both features are enabled by turning them on during
the tunnel creation process. They are enabled on a per-FCIP tunnel basis. See
on page 383 for details.
Constraints for Fastwrite and Tape Pipelining
Consider the constraints described in
Table 91 Using fastwrite and tape pipelining
Fastwrite
Each GbE port supports up to 2048
simultaneous accelerated exchanges, which
means a total of 2048 simultaneous
exchanges combined for fastwrite and tape
pipelining.
Does not affect FICON traffic
Does not support multiple equal-cost path
configurations (see
configurations" on page 381).
Table 21-5
"Supported
when configuring tunnels to use either of these features.
Tape pipelining
Each GbE port supports up to 2048
simultaneous accelerated exchanges, which
means a total of 2048 simultaneous
exchanges combined for fastwrite and tape
pipelining.
Does not affect FICON traffic
Does not support multiple equal-cost path
configurations or multiple non-equal-cost path
configurations (see "Supported
configurations" on page 381).
Fabric OS 5.2.x administrator guide 381
"Configuring FCIP tunnels"