On Fri, 17 Mar 2006 at 12:00pm, Salada, Duncan S (Titan) @ TITAN wrote
Something with no line breaks in the paragraphs. Please add some line breaks.
I'm having trouble getting amtapetype to give me a 200gb tapetype for a HP Ultrium LTO 1 drive. It tells me that hardware compression is on, and I've tried using "-e200g" with "-f/dev/rmt/0ubn" and "-f/dev/rmt/0cbn" in desperation. But it still will only give me the 100gb tapetype:
amtapetype writes random data, which does *not* compress. In days of yore, you'd get a smaller than expected tapelength if you wrote to a drive with compression on, because the data would actually expand when going through the hardware compressor. LTO drives are smart enough to know when data won't compress, and don't try to compress such data. Thus, your 100gb tapelength.
To use hardware compression with amanda, you essentially lie to amanda. Estimate how compressible your data is, and increase the tapelength from the native size by that amount. If you think your data really will compress to 50% it's original size, then set your tapelength to 200GB.
-- Joshua Baker-LePain Department of Biomedical Engineering Duke University
