Re: Compression Tape Drives

In article <2pgiio$sj0@emory.mathcs.emory.edu>, RDSENDEK+aSRBMIS1%SRBJG@mcimail.com ("ROY D. SENDEK") says: > > > >How would you set up a tape drive that uses data compression with the ONLINE ENGINE? >It is my understanding that you need to specify the tape size in the TBCONFIG file in KB. >Since the amount of data that the tape can store is dependant on the actual compression >ratio there is no way of knowing exactly how much will fit on the tape. > >I would appreciate any information on this since I plan on backing up to a drive that will >store from 5GB to 25GB depending on the compression. We use the time-honored method called "trial and error". Luckily, our Pyramid 8mm compressing drives have an LCD panel that tells how many GB are written to the tape. We look at that when the archive is 98% complete, and keep bumping the number in TBCONFIG up. When we get a premature EOF (and the archive bombs), we decrease the number. Not terribly pretty, but the compression ratio on a given database is fairly constant over time (at least for us). ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Jim Burks jburks@promus.com ~ ~ Database Administrator / Systems Engineer ~ ~ The Promus Companies, Inc. Memphis, TN USA ~ ~ http://stargate.promus.com/public/jbb.html ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~