My original message was:
"I made a vdump backup on a DEC TLZ6L-DA tape drive on my Alpha Server 4100
> (running DU 4.0D), and I'm now trying to restore these tapes on a Hewlett
> Packard SureStore Tape 6000 tape drive. Unfortunately, this doesn't seem
> to
> be working. I keep getting I/O errors when I try to do the restore or even
> show the contents of the tape. The exact error message that I get is this:
>
> vrestore: unable to use save-set; invalid or corrupt format
>
>
> ************* PROGRAM ABORT **************
>
> vrestore: can't obtain fileset attributes
>
>
> The type of tapes that I'm using are Hewlett Packard Digital Data Storage
> 2.
>
> I can successfully show the contents of these tapes on the TLZ6L-DA tape
> drive and also restore them. Does anyone have any ideas?"
>
>
>
I should have included my vdump command with this message. The problem had
to do with compression of the data on the tape. When I did my vdump, I
included the -C switch which includes compression. The full command that I
used to dump was:
# vdump -D -Cuv -f /dev/rmt0h <filesystem>
The command that I was using to restore from the tape was:
# vrestore -xv -f /dev/rmt0h -D <restore directory>
What I should have used for my dump command is:
# vdump -D -uv -f /dev/rmt0h <filesystem>
Here is an excerpt from a message that I received from Dr. Tom Blinn who was
able to explain this very clearly:
"The TLZ6L-DA does compression in the hardware by default if you use, for
example, the "rmt0h" drive name.
For tape drives, the mapping of drive names to "densities" (which for the
DAT
drives usually means "hardware data compression or not") is controlled by
the
entries in the Dynamic Device Recognition database (DDR). If there isn't
any
entry there for the HP SureStore Tape 6000 tape drive, then you probably are
going to get uncompressed; or the drive might not even support decompression
in the hardware, I don't know. But the compression/decompression algorithms
are industry standardized, so it's probably a matter of being able to get
the
HP drive to do decompression.
I can't tell you much more.. Most of the DAT drives that support hardware
compression and decompression "sniff" the media on reads and automatically
do
the right thing. What vrestore is seeing when you try to read the tape
isn't
what it expects -- the data looks like garbage, and this is what would
happen
if you tried to read a compressed tape on a drive that doesn't do
compression
and decompression in hardware, or isn't configured correctly to
automatically
enable decompression by "sniffing" the tape media."
Thanks to everyone else who responded!
-Stephen Spalding
Received on Thu Jan 14 1999 - 17:49:58 NZDT