[Hampshire] Tape drives - one can't read from t'other!

Hi all



At my wit’s end with this so hopefully someone with more experience can
help… Does anyone know why a tape written on a given drive will not be
readable on another drive when they’re the same format and being written /
read with the same method?



I’ve written a series of backup tapes (I know this is archaic technology but
I want write-once-read-many and I want something non-volatile – hence tape).
I’ve bought 2 drives: one SAS based which is doing the writing and, mindful
this is old technology, another SCSI based. The two drives are installed
in separate boxes. FWIW the working SAS box is running jammy and the
(apparently) working SCSI box is running noble though I suspect this makes
little difference.



Trouble is: the SCSI drive is flaky / mostly non-working reading only tapes
written by the SAS drive. I happen to have some pre-used tapes which were
written on a completely different drive (i.e. neither of mine made them) and
the SCSI drive can read them fine. Therefore, the SCSI drive, HBA and
cable are all fine. For some reason, it just can’t read the tapes I’ve
just written on the SAS box. And yes – the SAS drive can read back the
tapes it has just written itself.



So why would a LTO4 SCSI drive not be able to read from a LTO4 SAS drive
when it can read LTO4 tapes written on another machine?



FWIW the write command I’m using is:



tar czvf /dev/nst0 files_to_write



For reading, I use:



dd if=/dev/nst0 bs=1M | tar xzvf –



Both The read command works fine on the SAS drive to read its recordings
back (so I know the recording has worked) but if I take one such tape
(written on the SAS drive) and try to read it using the same command on the
SCSI drive – no dice – all I get is “Input / Output” error.



Things I’ve tried:

1.    A cleaning tape – seemed to go through its paces but no change
2.    Testing for it being a tar issue, I tried: dd if=/dev/nst0 bs=1M
of=fred.img

After a long period of tape activity, I get “Input / Output error” and
fred.img is 0 bytes long.



So in short, it looks like both drives are working fine but the SCSI one
can’t read tapes written on the SAS one – but can read tapes written on
other drives. FWIW the SCSI drive can read its own tapes.



Any constructive advice very welcome. With 20Tb SSDs being so pricey, HDDs
being mechanical, Cloud storage for 20Tb being laughably expensive – tape is
all I can think of for an archive format. And, of course, newer LTO
protocols are, again, beyond my price range. I believe we’re up to LTO9
now – but that’s ~£2k for the drive itself even if it would mean far fewer
tapes.



Cheers

R

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