Technical data

Fabric OS FCIP Administrator’s Guide 63
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Options for enhancing tape I/O performance
3
Options for enhancing tape I/O performance
FCIP Fastwrite and Open Systems Tape Pipelining (OSTP) are options available for enhancing open
systems SCSI tape write I/O performance. FCIP Fastwrite and OSTP are implemented together.
When the FCIP link is the slowest part of the network, consider using FCIP Fastwrite and OSTP. FCIP
Fastwrite and OSTP are two features that provide accelerated speeds for read and write I/O over
FCIP tunnels in some configurations:
OSTP accelerates SCSI read and 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. To use OSTP, you must also enable FCIP Fastwrite.
Both sides of an FCIP tunnel must have matching configurations for these features to work. FCIP
Fastwrite and OSTP are enabled by turning them on during the tunnel configuration process. They
are enabled on a per-FCIP tunnel basis. See “Creating an FCIP tunnel” on page 69 for details.
Consider the constraints described in Table 13 when configuring tunnels to use either of these
features.
TABLE 13 Using FCIP Fastwrite and OSTP
FCIP Fastwrite OSTP
Each GbE port supports up to 2048 simultaneous
accelerated exchanges, which means a total of 2048
simultaneous exchanges combined for Fastwrite and
OSTP.
Each GbE port supports up to 2048 simultaneous
accelerated exchanges, which means a total of 2048
simultaneous exchanges combined for Fastwrite and
OSTP.
Does not affect FICON traffic Does not affect FICON traffic
Does not support multiple equal-cost path
configurations (see “FCIP Fastwrite and OSTP
configurations”).
Does not support multiple equal-cost path
configurations or multiple non-equal-cost path
configurations (see “FCIP Fastwrite and OSTP
configurations”).
Class 3 traffic is accelerated with Fastwrite. Class 3 traffic is accelerated between host and
sequential device.
With sequential devices (tape drives), there are 1024
initiator-tape (IT) pairs per GbE port, but 2048
initiator-tape-LUN (ITL) pairs per GbE port. The ITL pairs
are shared among the IT pairs. For example, there are
two ITL pairs for each IT pair as long as the target has
two LUNs.
If a target has 32 LUNs, there are 32 ITL pairs for IT
pairs. In this case, only 64 IT pairs are associated with
ITL pairs.
The rest of the IT pairs are not associated to any ITL
pairs, so OSTP is not performed for those pairs. By
default, only Fastwrite-based acceleration is performed
on the non-associated pairs.
Does not support multiple non-equal-cost path
between host and sequential device