Dan Langille wrote (2016/03/13):
> > As well as increasing max file size you need to boost the tape buffer size 
> > from the 64kB default. I use 2MB
> 
> This is a hardware setting?

Hello, it is software settings:

* Increasing max file size is "Maximum File Size". I use 16 GB for
  LTO-5 and for LTO-4 it should be similar. Every file mark means delay
  of several seconds (3-5?), so you can count, how big slow down for
  each file size it is in percents. On the other side, too big file size
  means slower seeks.

* Tape buffer size: It is "Maximum Block Size". It seems that in Linux
  it is a must to increase it. However, in FreeBSD, I have no problems
  with default 65536 bytes, where I have seen speeds over 250 MB/s with
  well compressable datas and without notable system load, so I did not
  increase it yet. For check, how big block you can use, try mt status -v.
  It is smaller of maxio and cpi_maxio. Without kernel patching, you could
  certainly use 131072 bytes. However, maxio could be increased easily
  (MAXPHYS kernel option) and cpi_maxio depends on driver, how well the
  value is obtained. Sometimes it is just a constant, which is known that
  it could be increased. But, I still think that it is not needed so much
  in FreeBSD.

-- 
Rudolf Cejka <cejkar at fit.vutbr.cz> http://www.fit.vutbr.cz/~cejkar
Brno University of Technology, Faculty of Information Technology
Bozetechova 2, 612 66  Brno, Czech Republic

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