Another Tricky One!! - Media Question 1

[sgoldsmith]

All,

Say I write a backup to a brand new fresh tape (in one fragment, not multiplexed). This backup uses hardware compression. The image will reside from block 0 (or as near as possible, the tape header will take up a block or 2) to a random block further on the tape.

First question, how can I find out where on the tape that image has reached (in terms of "end block")?

Second part is, say I performed the same backup to another fresh, bramd new blank tape (again in 1 FRAG and no mulitplex). But this time there is little to no hardware compression available (because of using the software encryption). Is there a method or tool I can use to get the "real world" / physical difference in the size of the data on the two tapes?

This is the only way I can see of accuratley gauging how much of an impact the "lack" of hardware compressions costs in terms of media usage.

Any thoughts?

Simon Goldsmith
Storage Engineer

 

[comtec17]

For question 1, if this was a sun server, I would use rmt commands to view segments.

As for question 2, compression of files is dependant on the file itself. There is no way to tell how compression will do in ones environment unless all files are exactly the same.

 

[sgoldsmith]

Thanks comtec.... it is a Sun server, so I will look further in the rmt commands.

For question 2 - lets say the files are exactly the same. Indeed, they will be cause this will be a controlled test.

Simon Goldsmith
Storage Engineer

 

[OHWS]

Not sure if this is what you are looking for but the bpimmedia command can tell you what images are on the tape and where the image starts on the tape and where the image ends on the tape to the exact segments/fragments. We filter out alot of the data from this command to only get the fragment info and the date stamp along with the policy name.