Re: archive compression question

In article <46r3gn$5f9@news.xmission.com> dbaresrc@xmission.com (DBA Resources) writes: >From: dbaresrc@xmission.com (DBA Resources) >Subject: archive compression question >Date: 27 Oct 1995 17:05:27 GMT >We are looking at getting either a 4mm or an 8mm device to do OnLine >archives. Each of these devices has on-board hardware compression that >can double or triple the native capacities of the drives. >My question is this -- will the data stream coming out of the engine com- >press or is it like a gif file that is as compressed as it can get? What comes out of the engine is what's on the disk. If you have a lot of text data with a very skewed distribution of characters that will compress well. Data which is numeric with a large spread of values probably won't it would be more gif-like. I suspect that pages with index on them would be more gif-like as well. The real problem is that without experimenting you don't know what percentage of compression to expect. If you don't know what percentage compression to expect what do you tell the system is the effective length of tape? I think it would take an unacceptable proportion of your life trying to work it out. It might be easier if the tape drives had some sort of indicator of percentage of tape used. I don't know about 8mm but I havn't found a 4mm drive with that feature :-( (HP - are you listening?) Ian