[clug] LTO-4 drive, turn on compression?

Daniel Pittman daniel at rimspace.net
Mon Aug 10 19:02:09 MDT 2009

Chris Smart <mail at christophersmart.com> writes:

> Anyone know how to turn on compression on an LTO-4 tape drive?  Have tried:
> mt -f /dev/nst0 compression 1
> But that didn't work. The man page is not super helpful and my Google-fu sucks.

That should be it, sorry.  There isn't anything else *standard* to turn on
compression.  (Although the 'default compression' option /might/ be worth
checking, just in case...)

> I have a Quantum SAS connected LTO-4 drive which works a treat, but
> I'd like to backup more than 800GB onto a single tape.

Personally, my strong preference is to do the compression in software rather
than rely on the drive.  There is nothing like discovering that the one tape
drive that just failed was the /only/ one that can manage to decompress the
tapes it wrote, for some crazy reason.[1]

LTO tapes are better, in my experience, than the crappy old standards, but
I am still nervous about it all, and prefer to stick with software
compression.  (Typically, only LZO compression, because it is very fast and
reasonably effective.)

Using software also gives the backup software a better insight into just how
much compression it manages on average, and sometimes can do that before
dumping to tape.


[1]  In my experience, subtle misalignment issues being magnified by
     compression, so reading uncompressed tapes worked in another machine, but
     compressed ones didn't, and firmware version quirks.

✣ Daniel Pittman            ✉ daniel at rimspace.net            ☎ +61 401 155 707
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