ClearPath OS 2200 Series Release 13.2 Software Planning and ...

Tape and DVD
4.6.6. Linear Tape Open Ultrium LTO4-HP Tape Drives
The LTO4-HP is configured as a LTO4-SUBSYS tape subsystem.
Caution
Unisys supports LTO tape drives for audit devices. However, before
configuring a Step Control type audit trail to use either the LTO3-HP or
LTO4-HP drives, you should consider the potential impact on the application’s
recovery time. Application recovery times can be significantly impacted
depending upon the location (on the tape) of the recovery start point and the
number of LBLK$ operations required to position the tape during recovery.
Application programs, thread duration, audit volume, AOR action, and TCDBF
checkpoints will affect tape positioning and could push the combined Exec
and IRU short recovery times beyond fifteen minutes.
The LTO4-HP tape subsystem can be used either in a library or in a freestanding
environment. The subsystem supports both SCSI (Ultra 320) and fibre channel
connections to the host; however, OS 2200 systems only support the fibre channel. The
LTO4-HP subsystem can write to Ultrium 3 and Ultrium 4 cartridge media. A Generation
4 subsystem can read Ultrium 2 cartridges, but cannot write to them.
The Ultrium 3 media has an uncompressed capacity of 400 GB and a compressed
capacity of 800 GB. The Ultrium 4 media has an uncompressed capacity of 800 GB and a
compressed capacity of 1600 GB.
The Generation 4 subsystem uses the LTO-DC data compression format, which is based
on ALDC. The subsystem does not compress data that is already compressed.
The Ultrium 4 device transfers uncompressed data at 120 MB per second and
compressed data at 240 MB per second. The actual transfer rate is limited by the
channel connection and IOP type.
There are no density options. The Generation 4 subsystem writes at the density that is
appropriate for the media type being used.
Electronic partitioning (EP) is supported for the HP Ultrium 4 device.
The Generation 4 subsystem supports buffering, and Ultrium 4 devices include a 128-MB
cache buffer. Both Tape Mark Buffering Phase I (BUFFIL) and Tape Mark Buffering
Phase II (BUFTAP) are supported.
The LTO specification requires that a device can read and write the current generation
format (Ultrium 4) and one previous format (Ultrium 3). For the Generation 4 subsystem,
if an Ultrium 4 cartridge or Ultrium 3 cartridge is mounted, it can be read and written. The
Generation 4 subsystem cannot write to an Ultrium 2 cartridge, but it can read from it.
4–22 7831 0349–043