IBM TS4500, Введение и руководство по планированию

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increases the effective data rate performance from host servers that force
explicit synchronize operations during write operations.
Backhitchless backspace
Backhitchless backspacing enables some backspace operations to be
virtualized without physical back-hitching. If you write and overwrite
multiple trailer labels, this firmware feature provides major performance
improvements.
Capacity scaling
If you want to exchange capacity for improved access times, 3592 tape
drives support multiple format options, such as scaling and segmentation
modes. These tape drives can sense and report the scaling state of current
medium by using the SCSI Mode Sense command and specifying Mode
Page X'23'. Capacity scaling is only offered on the JB, JC, and JD media
types.
WORM
The 3592 tape drives support write-once-read-many (WORM) behaviors
and format attributes. Three WORM cartridge types are supported: JX
Extended WORM cartridge, JY Advanced Type C WORM cartridge, and JZ
Advanced Type D WORM cartridge. WORM cartridges are
factory-formatted as WORM cartridges and cannot be converted to data
cartridges. The TS1140, TS1150, and TS1155 tape drives allow append
operations to data already on WORM cartridges, but do not allow data to
be overwritten under any circumstances.
Constant Capacity-based and Maximum Capacity-based LEOT reporting
The TS1140, TS1150, and TS1155 tape drives use enhanced logic to report
logical end-of-tape (LEOT) data. The drive is configured to report LEOT
using either a constant capacity-based LEOT algorithm or a maximum
capacity-based LEOT algorithm. These drives use the constant
capacity-based LEOT reporting. Constant capacity-based LEOT reporting
monitors the number of data sets (i.e., physical records) written to the
medium and reports early-warning (EW) based on the number of data sets
written to tape (i.e., the number of data sets to hold the advertised native
capacity). This reduces the variation in the amount of data that is recorded
before EW is returned. For applications that stop writing upon receipt of
EW, a more consistent capacity is recorded to the medium. This process
allows tape copies to finish without overflow a higher percentage of the
time.
Enhanced format for recording error-correction codes (ECCs)
The logical formats of the TS1140, TS1150, and TS1155 tape drives offer
error-correction-code capabilities of two orthogonal Reed-Solomon ECCs
that protect the data on tape.
Drive mechanical and electrical reliability
The mechanisms of the TS1140, TS1150, and TS1155 tape drives are
specified at a mean-cycles-between-failure rate of 300,000 cycles, which is
the highest reliability rating in the industry. The mechanism contains
special mechanical and electrical features to prevent damage to the media
on power-down or reset. These features also prevent the dropping of the
leader pin or other thread failures during similar interruptions. It also
tolerates high vibration and shock environments without data loss or
degraded operation.
Data compression
The 3592 tape drives use the data-compression method that is known as
Chapter 1. Overview
23