FWIW: I had similar problems with a large batch of LTO5 tapes recently.

Discussion with the tech support guys at Overland brought out the 
information that sometimes they see this on new tapes due to dust 
contamination during assembly (or insufficient removal of loose 
particles during manufacture) but the tapes are usually ok after a 
couple of passes.

Apparently this is why they sell "pre cleaned" media for their changers 
- and there's also a healthy market for tape polishing machines amongst 
Big Tape users.

There was enough crud in this particular batch (HP tapes) to degrade one 
of the drives quite badly (down to under 800Gb recorded on 1500Gb raw 
capacity), so we swapped it out under support contract. The other drives 
in the changer all recovered by themselves.

Also: Because LTO media uses a serpentine layout, "rewind" doesn't do 
anything - the end of the tape is also the beginning of the tape. If you 
want a cartridge to spool end-to-end, you'll need to seek to end of media.

Cleaning tapes are abrasive. Don't use them unless the drive asks for 
them. LTO drives and media have internal head and path wiper mechanisms 
which keep things under control under normal circumstances - cleaning 
tapes are a last resort.


On 10/01/13 03:22, UserMOP wrote:
> It would seem the problem resolved itself.
>
> All our tapes are now getting full at 410GB and over. No tape is under 400GB 
> so far (about 10 of them swapped around). Do not believe it was tape drive 
> itself.
>
> All we've done to the machine was regular ubuntu upgrades and machine 
> restarts. Occasionally we would clean the drive with a cleaning tape (even 
> when not asked). In addition, we ran the tapes through rewinding and weof 
> process before running each nightly Full backup (did not bother to do this 
> for Differential sets).
>
> We are happy, atleast for a moment.
>   8)
>




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