HP LTO Ultrium 4 drives technical reference manual, volume 2: software integration 27
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4 Factors affecting performance
This chapter contains techniques and information to help you design software applications so that
they use the tape drive’s potential as efficiently as possible.
• Ways of optimizing performance:
• Ensuring the recommended minimum transfer sizes page 27
• Identifying the media type page 28
• Using Cartridge Memory instead of tape headers page 28
• Using the Performance Log page to diagnose problems page 28
• Time-out values to help you tune timings in backup applications page 28
• Log pages—recommended support page 29
• Factors affecting performance, relating separately to the host, drive and format page 29
Ways of optimizing performance
HP’s Ultrium drives are high-performance products. Application software may require significant
enhancement in order to capitalize on this speed. There are a number of areas to look at and these
are discussed below.
Further details can also be found in the “How to optimize the performance of hp ultrium tape drives”
white paper.
Detecting the drive’s speed
Applications should not key off Inquiry strings in order to tell the difference between different speed
drives. It is better to use the Performance Log page see under the
LOG SENSE command in Chapter
4, “Commands”, of SCSI Interface, Volume 3 of the HP LTO Ultrium Technical Reference Manual.
In the Performance Log page (34h), parameter 04h (Native data rate) gives the native data rate of
the drive in units of 100 KB/s. LTO 4 drives give the value 04B0h, indicating 120 MB/s with
Ultrium 4 media or no cartridge loaded. If a previous generation cartridge is loaded, the value will
be lower.
Ensuring the recommended minimum transfer sizes
Use the Data Compression Log page. HP cannot diagnose performance issues without accurate
reporting of the current compression or the average compressibility over a backup session. Make
sure that you report the log page.
Regarding HP’s One-Button Disaster Recovery (OBDR) feature (see “One-Button Disaster Recovery
(OBDR)” on page 89), it is important to note that in some situations the SCSI block size may have to
be fixed for a given tape for format reasons. This means that if the host writes 2 KB blocks to support
OBDR, it may have to continue to write 2 KB blocks for the rest of the tape; it depends on the format
compatibility required by the overall system. However as HP Ultrium drives are insensitive to
