This is related to a similar question I have been investigating on 3592 media: Why would you ever get less than the native capacity of a tape?
Does writing compressed data to tape with hardware compression enabled result in the data expanding? I always assumed that the hardware compression mechanism would have something equivalent to "CompressAlways=NO" and detect already compressed data in its input buffer, however we backup a number of already compressed file formats and often see FULL tapes with estimated capacities from 5 to 20% less than the stated native (uncompressed) capacity. Can anyone confirm this? Thanks. On Thu, 9 Dec 2010 16:30:18 0100, Hans Christian Riksheim wrote: If a LTO4 tape holds more than 800GB compression is on. > > At our place, file data only has a 1.1:1 compression while Oracle data and > mail is 2.5:1. Overall it is 2:1. > > Hans Chr. > > > On Thu, Dec 9, 2010 at 9:18 AM, Mehdi Salehi <[email protected]> wrote: > > > Hi, > > Drives are LTO4, devclass is ULTRIUM4C, but all "Full" volumes are between > > 800GB to 1TB. Is it normal? It seems TSM does not use compression. > > > > Mehdi > > > >
