On Thu, Apr 21, 2005 at 10:49:00AM -0400, Vicki Stanfield wrote: > > If the dump is 28GB, should it not fit on a 20GB tape if it is > compressed. Aren't the tapes basically 20/40GB?
Not in my mind. They are 20GB tapes. I.e. they can hold 20GB of ones and zero bits. What those ones and zeros represent "could be" 40GB of data compressed ton 20GB of zeros and ones. I.e. 50% compression. But the level of compression varies greatly with the type of data being compressed and the algorithm being used. In fact, the compressor used by your tape drive can actually expand some types of data rather than compressing it. Using gzip as the software compressor I've tested data and gotten 0, 3, 10, 25, 50, 75, even 90+ percent compression. If the data in your dump compresses 50%, fine, it will fit on a 20GB tape. But if it only compresses 3%, I doubt it. And if it was already compressed by gzip (or has lots of gzipped files), it WILL EXPAND if the tapedrive compressor works on it. -- Jon H. LaBadie [EMAIL PROTECTED] JG Computing 4455 Province Line Road (609) 252-0159 Princeton, NJ 08540-4322 (609) 683-7220 (fax)
