| Title: | Ask the Storage Architecture Group |
| Notice: | Check out our web page at http://www-starch.shr.dec.com |
| Moderator: | SSAG::TERZA N |
| Created: | Wed Oct 15 1986 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 6756 |
| Total number of notes: | 25276 |
Hi all,
I work in the E.S.C media room in Galway. A customer (Reuters)
sends in 2 tapes for duplication on TK50. They are tape 1 and tape 2 of
a save set. Tape 1 causes problems as the tape is already full and when
mastered and copied again, the copies usually (always) fail at 99% with
an end of tape error. We have found one TK50 drive out of 60 will
usually copy the long tape. It will put slightly more data onto the
tape if this drive is connected to a MVAXII rather than a 3600. It
will not copy at all at a block size of 183,966, but will copy at a
blocksize of 183855 and attached to the MVAX11. The duplication
software (imps) has a recomendation of not greater than 160000 or a
master tape not more than 90% full.
Recently we tried to overcome the problem by shortening a tape but
found that if approx 15 feet were removed from the tape it would not
work at all, it gave an "eot detected while read/write" error. If we
removed approx 6 feet we noticed that when doing an image backup to the
tape that the drive NEVER physically goes to the EOT mark. We are not
too sure why but it looks like there must be a hardware count in the
drive. Is there any way we can get round this problem? We are willing
to give anything a try. Any help or pointers would be greatly
appreciated.
Thanks and regards,
Noel P Browne.
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 6599.1 | TAPE::PETERS | Fri Apr 18 1997 13:47 | 11 | ||
Yes, the TK50 knows how long a tape is. If you change the tape length it will fail. I suggest you use SaveSet Manager ( SSM ) to make your duplicate tapes. It knows about savesets and can copy multi volume backups. Steve P. | |||||
| 6599.2 | SSM may not be full solution. | SIOG::BROWNE | Mon Apr 21 1997 06:48 | 15 | |
Thanks for the quick reply.
We are investigating the SSM suggestion, we had not been familiar
with SSM. However we do not se it completely fixing our problem. If it
does copy the first tape of the backup then each tape will have to be
done one to one and without the control of copying software (in our
case imps). There will also be the problem of verifying the copies. One
scenario may be if SSM could break up the first tape into two tapes and
then we could master both tapes and then imps could take control. (This
still leaves us with the problem of having to modify the customers tape
every time, something we could do without.) You say the TK50 "knows"
the length of the tape, how does it do this? Is the count on rom? Most
important (even if irregular) could we modify this? Any idea as to why
we have one TK50 which is regularly able to copy on more data than the
other? Again tkanks for any suggestions or help.
Noel P.
| |||||
| 6599.3 | Pad blocks | SSDEVO::JACKSON | Jim Jackson | Mon Apr 21 1997 10:53 | 18 |
My recollection (from being based adjacent to the TK50 development team in SHR) is that the TK50 will insert "pad" blocks in an effort to keep the tape streaming. If your host is just a little bit slow in getting the data to the TK50, it will insert the pad blocks, and you will get less data on tape. If your host can keep up, fewer pad blocks, more data blocks. If your host can't keep up, the tape has to reposition, fewer pad blocks, more data blocks, tape operations take an eternity. FYI, tapes traditionally do not have a "fixed" capacity. The problem that you are describing has plagued tape copy operations for at least 40 years. You either have to have a master tape that isn't full, or you have to use something like SSM and deal with it on a case-by-case basis. The TK50 development team was well scattered even before we sold the group to Quantum. -Jim Jackson former tape devo (but not TK50) | |||||