On Thu, 6 Sep 2007 09:14:17 -0400, Michael Coffin <[EMAIL PROTECTED]> wrote:
>We use 3590 B1A drives, with 10/30 carts providing native capacity of >10GB, with up to 30GB using hardware compression. I am under the >impression that the hardware will choose the best compression possible >UNLESS it is specifically told otherwise (i.e. via a TAPE COMP/NOCOMP >and DDR COMP/NOCOMP/LZCOMP options). Is this true, and is there a way >to query the hardware from z/VM (4.4) to see if default hardware >compression has been enabled on the drives (I imagine it has to be set >by the CE during install/configuration)? > >I have a z/Linux user that was trying to dump 13GB of data and ran out >of space, so it looks as though default hardware compression is not >working. :( > >-Mike IDRC compression is on by default, but can be turned off via software parameters. Some data is not well suited to compression, which may be the case with your user's Linux data. If the data being dumped is already in a compressed format the hardware compression is unlikely to compress it any further and may actually make it larger. This is a well known side effec t of many compression schemes. Brian Nielsen
