IBM L5X, Инструкция по установке и эксплуатации

Страница: 23 / 120

Speed matching
To improve system performance, the drive uses a feature called speed matching to
dynamically adjust its native (uncompressed) data rate to the slower data rate of a
server. With speed matching, the drive operates at different speeds when reading
or writing the Ultrium 4 or Ultrium 5 cartridge formats. Native data rates are
shown in the following table.
Table 4. Performance parameters
Ultrium generation media
Generation 5 media Generation 4 media Generation 3 media
Speed matching data
rates (MB/second) 140.0 120.0 80.0
130.0 113.1 76.1
120.0 106.0 72.3
112.7 99.2 68.4
105.5 92.3 64.6
98.2 85.3 60.7
90.9 78.5 56.8
83.6 71.4 53.0
76.4 64.6 59.2
69.1 57.6 45.3
61.8 50.7 41.5
53.5 43.8 37.6
46.3 36.9 33.8
40.0 30.5 30.0
If the server net (compressed) data rate is between two of the preceding native
data rates, the drive calculates the data rate at which to operate. Speed matching
reduces backhitch, the condition that occurs when a tape stops, reverses, and
restarts motion. A backhitch is usually the result of a mismatch between the data
rates of the server and the drive.
Channel calibration
System performance is further optimized by a channel calibration feature. With this
feature, the drive automatically customizes each read or write data channel to
compensate for variations in the recording channel transfer function, the media,
and the characteristics of the drive head.
Encryption
This drive supports host Application Managed Encryption (AME), using T10
encryption methods. However, encryption must be enabled through the software
application that you use to manage the tape drive. For more information about
enabling encryption, see the independent software vendor documentation that
came with your software.
Data encryption is supported only with LTO Ultrium 5 and LTO Ultrium 4 data
cartridges. The encryption-enabled drive contains the necessary hardware and
firmware to encrypt and decrypt host tape application data. Encryption policy and
Chapter 1. Product description
5