RE: Backup compression

["Andy Nolen-Parkhouse" <aparkhouse@xxxxxxxxx>]

Steven,

You can put 7GB worth of bytes onto each tape, whether or not these bytes
represent compressed stuff or not.  Compression will vary depending on
the type of objects being saved.  Your data file libraries, because they
probably contain lots of repeating blanks, will compress significantly.
Your program libraries will not compress as much.

It sounds like you're planning a full save.  Your calculations below are
accurate, although if you are getting 12GB on one tape from data
libraries, it wouldn't hurt to have a few extra tapes because your system
save and IBM libraries will not compress as much.

Regards,
Andy Nolen-Parkhouse

> On Behalf Of Steven.Gray@xxxxxxxxxxxxxx
> Subject: Backup compression
> 
> All,
> 
> The 6390 tape unit supports 7GB uncompressed upto 14Gb Compressed I
> have
> been informed , the question that I have is
> the 7-14Gb is there a direct relationship between this and the actual
> size
> of the data that will be saved onto the tape from my AS400?
> 
> i.e if I can get 12GB of data per tape , and my data on the AS400 is
> 120Gb ,
> does this mean that it will take 10 tapes to save all of this data?
> Or is there software aswell as hardware compression taking place?
> If this is so , how can predict how many tapes I will need for a given
> database size?
> 
> Regards
> 
> Steven Gray