gottlieb%bbn-unix@sri-unix.UUCP (01/13/84)
From: Arthur Gottlieb <gottlieb@bbn-unix> We are in the process of configuring a VAX 750 to run UNIX. DEC would dearly love to sell us a TU80 tape drive. The drive is supposed to be 25 ips start/stop and 100 ips streaming. We will be backing up RA81's (~400 Mbytes) and 25 ips is clearly unacceptable. Has anyone had any experience with these drives? Can they be made to stream under UNIX? Please send replies to gottlieb@bbn-unix. Thanks, Arthur
obrien%rand-unix@sri-unix.UUCP (01/14/84)
The only program I've ever personally seen that can run any DEC device to near its channel capacity is George Goble's "dbuf". This thing splits into three forks: one reads, the second writes, and the third coordinates and makes the other two "change ends" at appropriate times. Its commands are a subset of "dd"'s. So if you don't mind making image copies for backup (with something like 21 Fuji Eagle disk drives that's what George Goble does), "dbuf" will probably be able to make the streaming drive stay streaming most of the time. We've found that it's far safer to give "dbuf" an exact count rather than letting it get a read error at the end of a partition. We're not sure why this is so but I thought I'd mention it while I'm on the subject.
cak@Purdue.ARPA (01/15/84)
From: Christopher A Kent <cak@Purdue.ARPA> There's a TU80 on campus now, attached to a new 780; it won't stream, even in standalone restore mode (building 4.2bsd from a tape). Don't get one. Cheers, chris ----------
thomson@utcsrgv.UUCP (Brian Thomson) (01/16/84)
We have a 750, 3 RA81s, and a TU80. The only time we have ever seen
it stream at 100 ips is when we tell it to skip records (i.e. mt fsf).
'dbuf' is not useful because you can't use it for multivolume dumps,
and only the smallest RA81 partition image will fit on a 2400 foot tape
at 1600 bpi.
--
Brian Thomson, CSRG Univ. of Toronto
{linus,ihnp4,uw-beaver,floyd,utzoo}!utcsrgv!thomsonandree@uokvax.UUCP (01/22/84)
#R:sri-arpa:-1544200:uokvax:6200013:000:786 uokvax!andree Jan 20 22:18:00 1984 I've got a tu80 and an ra81. As previously stated, Unix can make the tu80 go into streaming mode. If you don't mind having small file systems (~40 meg) so you can do image backups, a plain vanilla dd will do the trick. Since I don't have source, and don't have small file systems, I'm still trying to figure out how to get backups to put the tape in streaming mode (any help will be appreciated). I'm going to play with this problem some more this weekend/next week. I'll post results when I get them. BTW - I asked the local DEC CE (there are apparently 4 750/tu80/r?8? flavor systems around, all fairly new) if VMS provided a backup utility that would use the tu80 streaming mode. The reply was "don't know." I translate that as "probably not." Hard information is desired. <mike