Malcolm Wright
Well-known member
Hi,
I don't know how indicative this is of the compression schemes used by various tape drives hardware and backup software, but I thought I'd do a little test of how much I could compress p2 data with winrar.
With MXF files, the test yielded a reduction in file size of 11 %... not a whole lot, but significant if you consider you'll be saving one out of ten archival tapes at that rate of space economy.
The audio files compressed more, yielding a reduction in file size of 37 %
I compressed a full-to-capacity 4gb p2 card file structure containing 720/24pn footage, and the overall reduction in file size was of 16.7 percent.
I used the 'normal' setting in winrar, which is a compromise between fast compression time and small file size. Knowing that the hardware compression must occur pretty much on the fly, I thought this would be the most realistic setting for the test.
So its a tough call. On the one hand, almost 17 percent space saved means saving 1 out of 6 tapes. On the other hand, switching compression on probably slows archival speed considerably, and on tape drives where this is an issue (like my AIT), probably causes more stream to tape speed discrepancies, resulting in eventually damaging start and stop procedures on the part of the tape transport.
I'm going to stick with compression for the rest of this cartridge so that I can see just how much it ends up holding. And I think I'll stick with compression afterwards as well. I've read AIT transport speed is so low (less than an inch per second), that the stoping and starting is far less of a strain on the mechanisms than it used to be for DLT and other fast moving media.
M.
I don't know how indicative this is of the compression schemes used by various tape drives hardware and backup software, but I thought I'd do a little test of how much I could compress p2 data with winrar.
With MXF files, the test yielded a reduction in file size of 11 %... not a whole lot, but significant if you consider you'll be saving one out of ten archival tapes at that rate of space economy.
The audio files compressed more, yielding a reduction in file size of 37 %
I compressed a full-to-capacity 4gb p2 card file structure containing 720/24pn footage, and the overall reduction in file size was of 16.7 percent.
I used the 'normal' setting in winrar, which is a compromise between fast compression time and small file size. Knowing that the hardware compression must occur pretty much on the fly, I thought this would be the most realistic setting for the test.
So its a tough call. On the one hand, almost 17 percent space saved means saving 1 out of 6 tapes. On the other hand, switching compression on probably slows archival speed considerably, and on tape drives where this is an issue (like my AIT), probably causes more stream to tape speed discrepancies, resulting in eventually damaging start and stop procedures on the part of the tape transport.
I'm going to stick with compression for the rest of this cartridge so that I can see just how much it ends up holding. And I think I'll stick with compression afterwards as well. I've read AIT transport speed is so low (less than an inch per second), that the stoping and starting is far less of a strain on the mechanisms than it used to be for DLT and other fast moving media.
M.