Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site bu-cs.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!harpo!decvax!genrad!mit-eddie!think!harvard!bu-cs!root From: root@bu-cs.UUCP (Barry Shein) Newsgroups: net.unix-wizards Subject: Re: tar.c & blocksize Message-ID: <452@bu-cs.UUCP> Date: Sun, 30-Jun-85 21:02:03 EDT Article-I.D.: bu-cs.452 Posted: Sun Jun 30 21:02:03 1985 Date-Received: Fri, 5-Jul-85 02:43:48 EDT References: <203@geowhiz.UUCP> Organization: Boston Univ Comp. Sci. Lines: 28 >From: lm@geowhiz.UUCP (Larry McVoy) >Subject: tar.c & blocksize >... >My question is this: is it asking for trouble to play with the NBLOCK >definition in tar.c? Some people here have raised the question of >compatability, ie. what about other sites, what if they don't have source >and/or can't get a hacked version of tar? On the other hand, it seems that >the savings in time are great enough to warrent a change. > >If you have an opinion on this, I'd like to here it. > >-Larry McVoy [ARPA] mcvoy@wisc-rsch.arpa > [UUCP] ...!uwvax!geowhiz!lm As discussed before, there is already a problem. The default blocksize for 4.2bsd tar creates a tape that (as far as I can tell) can not be *physically* read by the tape drive on my SYSV/3B5 due to controller limitations. Making it larger, however, makes it no worse :-) I would suggest you warn your users or, better, not make it the default. You should probably warn your users anyhow, I suggest going no larger than 5 (tar cb 5 ...) if you really don't know who is going to read this tape. As an aside, I still swear I blew the circuit breakers twice on my TU78 by specifying a block size of one at 6250. (Data General also makes it tricky to read tar tapes with physical blocks larger than 8192 though it can be done.) -Barry Shein, Boston University