One of the common issue I had back when doing tape backup was head
alignment, it only had to be a fraction out and then you had the
situation you have now. I know some drive did have a slight bit of
alignment option but not knowing it it up or down left or right it would
be a bit of trial and error (even slackening the securing screws and
retightening the screw might be enough. The other point to check is how
clean is the head, it might need a clean.
Tim H
On 04/10/2024 12:06, rmluglist2--- via Hampshire wrote:
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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