I am talking about bottlenecks on reading from the tape. Sending the data to /dev/null eliminates any write bottlenecks and we still max out at 60mb/sec on a 250mb/sec drive.
Edit: Hrm. I believe you can disable hardware compression on some LTO drives. Maybe that would help?
There have been multiple attempts over the years to implement all sorts of algorithms but they have all failed to gain traction. For example Wavelet based compression works fantastically well for some data (i.e. real signals with band limited frequencies), and catastrophically badly for others (earth models defined with piecewise functions containing non-differentiable points). Some people are happy with lossy compression, others are not.
The only compression I have seen worth anything is in deep water, where there is literally no data in the water column (i.e. 500 consecutive zeroes in a 6000 byte block), gzip gives you the that section free.