Intel AS/400 RISC Server, 170 Servers, 7xx Servers manual Data To Save Hours

The following measurements were done on a system with newer hardware including a 3580 Ultrium 3 4Gb Fiber Channel Tape Drive, 571E storage adapters, and 4327 70GB (U320) DASD.

Save to Tape Vs. Save to Virtual Tape then DUPTAP to Tape

570, 8 Way, 96GB Memory, 305 DASD units for Virtual Tape Drives

Restricted State Save to Tape Restricted State Save to Virtual Tape Non Restricted DUPTAP

	4
Data	3.5
	3
TB of	2.5
1
to Save	2
	1.5
Hours	1
	0.5
	0	Save to Tape		Save to Virtual			User Mix Save		User Mix Save	to Virtual Tape	then DUPTAP
	Large File		Large File		Tape then	DUPTAP		to Tape

Save to Tape Vs. Save to Virtual Tape then DUPTAP to Tape

1000 Empty Libraries

3580 Ultrium 3 4Gb Fiber Tape Drive, 5761 4Gb Fiber Adapter

571E Storage Adapters, 4327 70GB (U320) DASD

305 DASD units for Virtual Tape Drives

			570, 8 Way, 96GB Memory
	30
Data	20
to Save
	10
Minutes
	0	Save to Tape	Save to Virtual Tape then DUPTAP

Restricted State Save to Tape	Restricted State Save to Virtual Tape
Non Restricted DUPTAP

Measurements were also done comparing save of 1000 empty libraries to tape versus save of these libraries to virtual tape followed by DUPTAP from the virtual tape to tape. The save to tape was much slower which can be explained as follows. When data is being saved to tape, a flush buffer is requested after each file is written to ensure that the file is actually on the tape. This forces the drive to backhitch for each file and greatly reduces the performance. The DUPTAP command does not need to send a flush buffer until the duplicate command completes, so it does not have the same performance impact.

IBM i 6.1 Performance Capabilities Reference - January/April 2008
© Copyright IBM Corp. 2008	Chapter 15. Save/Restore Performance	256