HP LTO 4 SCSI, LTO 4 FC, LTO 4 SAS manual Drive-related factors, Recommendation

Performance Factor	Detail
Recommendation:	• Try not to put Ethernet in the way of data transfer unless staging
	technology is being used; aggregation of multiple Ethernet clients
	remains a good strategy to delivering on drive performance.
	• Even with Gbit Ethernet, the effective throughput is less than that of
	an LTO Ultrium 4 drive, so either use carefully designed topologies,
	or stage an image first and use locally attached tape, otherwise the
	Ethernet itself can become the bottleneck.
	Gbit Ethernet can be used in a carefully designed topology.
	Alternatively, stage an image first and then use locally attached tape
	for the backup.
Write Commands	Do not interleave write commands with other commands, such as READ
	POSITION and LOG SENSE. Do not, for example, attempt to read the
	TapeAlert log page during a long write.

Drive-related factors

Performance Factor	Detail
Drive’s SCSI	In order to minimize SCSI bus loading, the drive must execute its SCSI
Performance	phases quickly. The phases are as follows:
	•	Selection
	• Message-out identification
	• Receipt of the command
	•	Disconnection
	• Mid-command bus-free time
	•	Arbitration and reselection
	• Message-in identification
Recommendation:	The host must always ensure the following:
	•	Disconnects are enabled
	• Synchronous negotiation is enabled and established between the
		drive and the HBA
	• The drive is in buffered mode
	• When reading and verifying, always use the same block size as
		that in which the tape is written, otherwise performance will be very
		seriously affected.
Transfer Mode	The transfer mode can be fixed or variable, selectable through the
	MODE SELECT command.
	Fixed Mode: The transfer size is equal to the (block) size multiplied by
	the number of records (blocks) in the transfer.

HP LTO Ultrium 4 drives technical reference manual, volume 2: software integration 31 HP restricted