>Recently we purchased two Exabyte 8500c tape drives. These tape drives,
>unlike the "Exabyte 8500" tape drive, are equipped with Exabyte's
>long-awaited compression board (based upon one of IBM's compression
>algorithms) which is supposed to raise the capacity of an 8mm tape
>anywhere from 5 to 25 GBytes, depending on the type of data being
>backed up.
>
>Currently, we are running AFS 3.2 in an exclusive Risc/Ultrix environment.
>Running "fms" on this tape drive produced the following output:
>
>Tape capacity is 102945767424 bytes (~100 GB !!!)
>File marks are 84912587 bytes ( ~81 MB !!!)
fms uses a zeroed 16k buffer for writing to tape. As you can imagine, you can
put a lot of compressed zeros on a tape. For those of you with source code, I
have a suggestion that makes fms much more accurate. Have it preinitialize the
buffer with a file. Before running fms, load that file with an existing
"compressed" file. I finally got accurate worst case numbers for our tape drive
using this method. The tape mark size will be more accurate as well. Of
course, if the backup program could write until EOT ...
