LTO drive unable to find end of data...

[Ruth Ivimey-Cook]

I keep having this problem: I have 3x LTO tape drives connected directly to my Server (two SCSI, one SAS). The drives work fine with Bareos most of the time. However if I shut down the server, even if the drives are idle and the shutdown uses the 'shutdown' command, there is a high (almost certain but not quite) chance that the tape in the drive at the time will become un-appendable thereafter, with this message:

02-Feb 21:00 helva-sd JobId 10389: Volume "Incr-04" previously written, moving to end of data.
02-Feb 21:13 helva-sd JobId 10389: Error: Unable to position to end of data on device "LTODrive1" (/dev/tape/by-id/scsi-30001438010af988a-nst): ERR=backends/generic_tape_device.cc:197 ioctl MTEOM error on "LTODrive1" (/dev/tape/by-id/scsi-30001438010af988a-nst). ERR=Input/output error.

02-Feb 21:13 helva-sd JobId 10389: Marking Volume "Incr-04" in Error in Catalog.

The error message is quite correct - the drive can no longer find end of data on that tape. My intent therefore is to prevent that from becoming the case.

I have found that it is possible to write a new EOF pair on the tape if you carefully position the head using 'fsf' commands, after which the tape behaves normally again. Also, on overwriting it the tape behaves perfectly.

The tapes are configured very similarly... for the one involved in the message above:

Storage {
  Name = "LTO4-I-Tape"
  Address = "helva"
  Password = "[md5]"
  Device = "LTODrive1"
  MediaType = "LTO4-I"
}

... and ...

Device {
  Name = LTODrive1
  DeviceType = tape
  Media Type = LTO4-I
  Drive Index = 0
  Autochanger = no
  AutomaticMount = yes
  AlwaysOpen = yes
  Archive Device = /dev/tape/by-id/scsi-30001438010af988a-nst

  Two Eof = yes

  RandomAccess = no
  RemovableMedia = yes
  Offline On Unmount = yes
  Spool Directory = /var/spool/tapespool/Drive1

  Maximum Block Size = 512k
  Maximum File Size = 32g
  Maximum Network Buffer Size = 65536
  Maximum Concurrent Jobs = 1
}

You will notice I have 'two eof' set, which was my hope that it would by default set end of data every time it completed a write, that is at end of each tape 'file' it would write eof, eof, then bsf back over the second eof so as to overwrite it as soon as the next file was written and thus ensure there was always an eof pair at end of current data. That doesn't appear to be happening though.

'Offline on unmount' causes the tape to eject (which I need), which is nice, and 'always open' stops it doing lots of rewinds, which is also necessary.

Any ideas how to solve this, so a server shutdown doesn't do nasty things?  I have contemplated an on-shutdown systemd script for the storage to do something. Might that help?

Regards,

Ruth

-- 
Software Manager & Engineer
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