Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!aplcen!haven!uvaarpa!mcnc!rti!dg-rtp!dg-rtp.dg.com!hackwort From: hackwort@dg-rtp.dg.com (Brian Hackworth) Newsgroups: comp.unix.admin Subject: Re: Dumping to an exabyte tape drive Message-ID: <1990Sep11.153044.165@dg-rtp.dg.com> Date: 11 Sep 90 15:30:44 GMT References: <439@cfa.HARVARD.EDU> <776PKVH@dri.com> Sender: usenet@dg-rtp.dg.com (Usenet Administration) Reply-To: hackwort@dg-rtp.dg.com (Brian Hackworth) Organization: Data General Corporation, Research Triangle Park, NC Lines: 63 In article <776PKVH@dri.com>, braun@dri.com (Kral) writes: |> In article <439@cfa.HARVARD.EDU> wyatt@cfa.HARVARD.EDU (Bill Wyatt,OIR) writes: |> > |> >I think you'd better concede the last 10% or so, as long as dump can't deal |> >with EOT. And even if it could, I once had a nasty surprise when restore |> >broke because a multi-volume dump (9-track in this case) did't start at the |> >beginning of the tape. |> > |> |> So the $64k question now is: why can't dump properly deal with end of tape? |> It's not like it's a new technology or something. |> |> Another (I suppose this one is only an $8k question): I'm not sure what you |> mean about the multi volume set above? How did dumps behavior cause the multi |> volume dump to start not at BOT? |> This whole discussion points out two serious flaws in the BSD dump: 1. It doesn't handle end-of-tape. You're right, this isn't new technology. It is fairly hard to add to dump, though, due to the way the program is designed. 2. Adding new devices, especially high-capacity cartridge drives, is difficult because you must figure out how to trick dump into giving correct estimates. For DG's version of dump, we have rewritten BSD dump to address these issues (and others) by (a) recognizing and sanely handling EOT, and (b) providing a table of dump devices which lists a name for the device, the blocking factor, and the capacity (such as "150M" or "2.2G"). Together, this allows you to add one line to one file describing the advertised capacity of the tape. If, because of IRGs or bad media, the actual capacity of some of the tapes is less than the advertised capacity, it's not a catastrophe because dump handles the EOT correctly. So, to answer the questions: For $8K: some sites may choose to put more than one dump on a single 8mm tape. This makes a lot of sense for dailies and even weeklies. As a result, any given dump file may not start at the beginning of the tape. For $64K: some versions of dump do deal with end of tape. I think they all should. -- Brian Hackworth Data General Corporation hackworth@dg-rtp.dg.com 62 T. W. Alexander Drive {backbone}!mcnc!rti!dg-rtp!hackworth Research Triangle Park, NC 27709 (919) 248-6143