On Tue, 2003-01-14 at 13:56, Jon LaBadie wrote: > Because something is wrong or you have a very old version of tapetype. > > Your drive specs will include a speed rating, in MB/sec probably. > Divide that into your tape's rated capacity to get an approximation > of how long it will take to write a complete tape. Tapetype should > take about twice as long as it makes 2 passes. > > Be sure in your calculation that you use matching speed and capacity > numbers. Matching in the sense of both refering to HW compression on > or both refering to HW compression off.
Jon, I am using the tapetype that came with 2.4.2p2 (from the Debian package). I am using GNU mt 2.5, which does not have a "comp" command like the BSD version. The closest I can see is "datcompression", but this is not a DAT drive. Nevertheless, querying my drive with: # mt -f /dev/nst0 datcompression yielded: Compression on. Compression capable. Decompression capable. I set datcompression off, but I don't know what effect that will have since this really isn't DAT drive. The Compaq SDLT320 is rated at 16 MB/s native, but with SDLT 110/220 tapes, I'm assuming the speed will drop back to that of the SDLT220 drive, which is 11 MB/s. So with a 110GB native capacity (112640 MB; 1GB=1024MB), that computes to 10240 seconds (2h 50m) to write a full tape with no H/W compression. Doubling that for two passes means tapetype *should* finish in 5h 40m. However, the first pass of tapetype took 304793 seconds to write "3513152 32Kb blocks in 103328 files", which is a paltry 368 KB/s. That is a large discrepancy in expected vs. actual performance. Eric
