HP A7533A HP StorageWorks Fabric OS 6.1.1 administrator guide (5697-0235, Dece - Page 394

fastwrite flows may be passed through the FCIP tunnel, but only if the FCIP fastwrite option is disabled on the tunnel. FCIP fastwrite and tape pipelining When the FCIP link is the slowest part of the network, consider using FCIP fastwrite and tape pipelining. Supported only in Fabric OS 5.2.x and later, FCIP fastwrite and tape pipelining are two features that provide accelerated speeds for write I/O over FCIP tunnels in some configurations: • FCIP fastwrite accelerates the SCSI write I/Os over FCIP. • Tape pipelining accelerates SCSI write and read 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 tape pipelining, you must also enable fastwrite. • Both sides of an FCIP tunnel must have matching configurations for these features to work. FCIP fastwrite and tape pipelining are enabled by turning them on during the tunnel configuration process. They are enabled on a per-FCIP tunnel basis. See"Managing FCIP tunnels" on page 409 for details. Constraints for FCIP fastwrite and tape pipelining Consider the constraints described in Table 89 when configuring tunnels to use either of these features. Table 89 Using FCIP fastwrite and tape pipelining FCIP 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. 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 affect FICON traffic FCIP fastwrite and FC fastwrite are mutually exclusive. Does not support multiple equal-cost path configurations (see "FCIP fastwrite/tape pipelining configurations" on page 395). Tape pipelining uses FCIP fastwrite, not FC fastwrite. Does not support multiple equal-cost path configurations or multiple non-equal-cost path configurations (see "FCIP fastwrite/tape pipelining configurations" on page 395). 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: Two ITL pairs for each IT pair as long as the target has two LUNs. If a target has 32 LUNs, 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 no tape pipelining is performed for those pairs. By default, only fastwrite-based acceleration is performed on the unassociated pairs. Does not support multiple non-equal-cost path between host and sequential device 394 Configuring and monitoring FCIP extension services