8mm tape device driver block size settings on the IBM RS/6000

[Joseph Gallagher]

	Just a few questions on RS/6000 tape device block size settings.

1) All IBM updates on the 8mm media are written with the block size set to
512 bytes.  'If' all the 8mm tapes IBM sends out are written with this setting
why are many RS/6000's shipped with these settings set to 1024 bytes?

2) I see that one of the options for setting tape device block size is
(0=variable lenght).  If a tape were made with the block size setting set
to '0' would another RS/6000 with its block size set to 512 or 1024 be able to
read the tape, or would its setting have to be '0' as well? 

	For those of you who don't know why this matters ....   

   If an 8mm tape is written with the tape device block size set to 1024 and 
you try to read the tape on a device whose block size setting is 512 bytes 
you will most likely get the following error message:
'Restore: Cannot read backup media....'
The reverse is true also.  Most people would assume from the message above that
the media was faulty, which is not the case here.

 	Any input on the above questions would be greatly appreciated.

With thanks,

Joseph Gallagher          E-mail: jgallagh at oracle.nl or jgallagh at oracle.com
Oracle Europe,
Dublin, IRELAND.