Data Compression - HP StorageWorks SDLT Series Reference Manual

Introduction

Data Compression

The SDLT drive reads and writes both uncompressed (native) and compressed
data.
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When operating in compressed mode, data capacity is affected by how much the
data can be compressed. Most data can be compressed at an approximate 2:1 ratio.
This would provide the SDLT 220 drive with a compressed capacity of 220 GB
and a compressed data transfer rate of 22 MB/s. The SDLT 320 has a compressed
capacity of 320 GB and a compressed data transfer rate of 32 MB/s.
The SDLT drive ships from the factory with data compression enabled for writing.
In this mode, data is always compressed when writing to the tape, but the drive is
capable of reading both compressed and native tapes. For the drive to write native
data, the data compression setting must be changed through the software. To
change the setting, consult the backup application software documentation for the
data compression enabling and disabling procedure.
Note:
depending on actual data, media condition, and system and controller capabilities.
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The SDLT 220 drive features a native formatted capacity of 110 GB and a
sustained native data transfer rate of 11 MB/s.
The SDLT 320 drive features a native formatted capacity of 160 GB and a
sustained native transfer rate of 16 MB/s.
Capacity may vary based upon actual stored data. Data transfer rates can vary
SDLT Tape Drives Reference Guide