Path: utzoo!attcan!uunet!mcvax!hp4nl!eutrc3!wzv!wietse From: wietse@wzv.UUCP (Wietse Z. Venema) Newsgroups: comp.unix.microport Subject: Re: Efficient tape I/O with 386/ix; How?? Keywords: streaming tape interactive slow Message-ID: <169@wzv.UUCP> Date: 12 Dec 88 19:45:21 GMT References: <317@focsys.UUCP> Reply-To: wietse@wzv.UUCP (Wietse Z. Venema) Organization: Eindhoven University of Technology, The Netherlands Lines: 30 In article <317@focsys.UUCP> larry@focsys.UUCP (Larry Williamson) writes: >Streaming tape I/O with 386/ix seems to be rather slow. The drive >is not streaming very well. It spends most of it's time stopping >and starting. I'm using an Everex Excel 60 with a long controller >card. You may consider using the ddd command that was posted earlier this year in one of the source groups by Tapani Lindgren . The following is an excerpt from the man page: Ddd works almost the same way as dd(1), but it has a much better throughput, especially when used with slow i/o- devices, such as tape drives. The improvement is achieved mainly by dividing the copying process into two processes, one of which reads while the other one writes and vice versa. Also all code conversion capabilities are omitted. There is no additional overhead copying data between various conversion buffers. Ddd was inspired by the vast difference in speed between BSD4.2 and BSD4.3 dumps - in BSD4.3 dump(8) writes to raw magnetic tape with several processes, thus keeping the tape continuously in motion. I wanted to get the same improvement to remote dumps, so this filter was needed. Adding it to any pipeline of commands usually increases the throughput (that is, if you have enough MIPS). -- work: wswietse@eutrc3.uucp | Eindhoven University of Technology work: wswietse@heitue5.bitnet | Mathematics and Computing Science home: wietse@wzv.uucp | 5600 MB Eindhoven, The Netherlands