I'm glad you corrected because when they worked, they were awesome. When they didn't, life had a lot of swearing in it... And when I was sysadmin for the MicroVAX II that had them, I swore like a sailor.... Warner On Mon, Oct 15, 2018 at 3:04 PM Clem Cole wrote: > #$%^ - they >>weren't<< like DECtape from a reliability standpoint ... > ᐧ > > On Mon, Oct 15, 2018 at 5:00 PM Clem Cole wrote: > >> Be careful, TK-50 is different than 9-track. It's a streamer tape like >> QIC, 4mm and 8mm. The blocking is done under the covers by the HW and the >> blovk size if just how a DMA is done. I recommend that you pre-fetch the >> read with dd or double-dd setting ibs=64k, obs=20b and conv=sync and pipe >> the output to the reader (tar/cpio or the like) [if that fails try >> obs=1b]. This should work well as can (TK-50 overall suck - don't set >> your hopes high on anything with them -- they were DECtape from a >> realiabilty standpoint, they were different from the reset of the world, >> the performance was poor and they were expensive). >> >> Anyway, by using dd or the like a front end, it will allow the read >> streamer to read as fast as it can. The problem is that the way it works >> under the cover does not shine with traditional UNIX I/O. BTW: ibs of >> anything more than 64K on a VAX (or PDP-11) will not help because of the >> dma size on the Unibus caps DMA read/writes at 64K. On a PMAX or (under >> Tru64 on a Alpha), you can try using really large ibs sizes depending on >> your physical memory size. >> >> BTW: What will help the most is actually finding a copy of the old >> double-dd program (from the UUNET archives) which forks off two child >> procees to perform the actual I/O and alternates between the two processes >> via pipe between them and controller - so one dd process is reading when >> the other dd process is writing. [It used to be called: ddd before the >> Gnu guys grabbed that name for the debugger]. The command line might be >> something like: ddd ibs=64k obs=20b | tar xvpf - >> >> FWIW: I wrote a version of a fast dd years ago that used pthreads and a >> semaphore that I should still have kicking around. At one point when I >> was dealing with streamer tapes for backup, I definitely ran it on Tru64 >> and FreeBSD, but I've forgotten where Ultrix fell. >> ᐧ >> >> On Mon, Oct 15, 2018 at 4:01 PM Warren Toomey wrote: >> >>> All, I received this request from Matthew who isn't subscribed to either >>> the TUHS or cctalk lists. He knows how to read the lists archives. Many >>> thanks for any help you can provide. >>> Cheers, Warren >>> >>> ----- Forwarded message from Matthew Whitehead ----- >>> >>> Date: Mon, 15 Oct 2018 08:25:39 -0400 >>> From: Matthew Whitehead >>> Subject: Ultrix Tape Blocks >>> >>> Warren, >>> I wonder if you can give me a referral. I want to install Ultrix-32 >>> on my MicroVAX II using the ancient TK-50 tape drive. I know the tape >>> files are on your archive, but I need to know the block size for each >>> of the many files; it can vary a lot. >>> Who might be able to help me with this? >>> Matthew Whitehead >>> >>> ----- End forwarded message ----- >>> >>