HP LTO Ultrium 6 tape drives UNIX, Linux and OpenVMS configuration guide

sizes that are no larger than 256 KB. Please check your application documentation to find out
how to check or configure block sizes used for transfers to and from tape or VTL devices.
This is because, by default, the HP-UX stape driver processes a block size larger than 256 KB by
subdividing it into 256 KB blocks for writing to tape (giving a net effect of 256 KB I/O transfers)
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.
For example a 1 MB block (1048576 bytes) is written to tape as four 256 KB blocks. During
restore, stape attempts to reconstruct the original block size that was larger than 256 KB with the
256 KB blocks from tape. This subdivision and subsequent reconstruction process of block sizes
larger than 256 KB adds unnecessary complexity and risk to tape positioning and restore operations
and offers no net gain in terms of increased block size. It should therefore be avoided.
What next?
Once device files have been created, you should confirm that your new tape drive is working
properly. “Verifying the installation” (page 25) provides instructions on backing up and restoring
a sample file to test your installation.
6. The maximum block size limit of 256 KB (262144 bytes) applies to all versions of HP-UX and is strongly recommended
for broad backup/restore compatibility across all supported HP-UX versions. Different HP-UX kernel configurations or
later versions of HP-UX may not use 256 KB ‘chunks’ as described; however all HP-UX versions and kernel configurations
are compatible and interoperable with a block size limit of 256 KB.
What next? 11