Path: utzoo!yunexus!gen1!tyler
From: tyler@gen1.UUCP (Tyler IVANCO)
Newsgroups: comp.sys.nsc.32k
Subject: Streaming and other things (was Re: ulimit() broken on ICM systems)
Keywords: INFO-ICM ICM nsc
Message-ID: <325@gen1.UUCP>
Date: 1 Feb 88 04:11:29 GMT
Article-I.D.: gen1.325
Posted: Sun Jan 31 23:11:29 1988
References: <1558@mmm.UUCP> <976@nscpdc.NSC.COM>
Reply-To: tyler@gen1.UUCP (Tyler IVANCO)
Organization: gen1 - York University, Petrie Bldg, Downsview, Ontario CANADA
Lines: 69

In article <976@nscpdc.NSC.COM> joer@nscpdc.UUCP (Joe Rawlings    ) writes:
>In article <1558@mmm.UUCP> schultz@mmm.UUCP (John C Schultz) writes:
>
>>and the poor streaming capability of the tape drive.  I have asked Natl for
>>a little help on these performance issuses which has resulted in a 
>>resounding "thud".
	The Sun 3/50 didn't stream until I used my little routine below.
>
>There are ways to improve performance of several of the different 
>UNIX utilities (tar, cpio, etc.), There is no way to improve the 
>limitations of the devices used (SCSI only goes so fast, cartridge 
>tapes can only APPROXIMATE streaming, etc.).
>

	I believe that this is a problem of the operating system getting
in the way of the I/O from/to disk/tape.  On the UofT 4.2 port for the
ICM, it is quite easy to stream the tape drive using tar with a large
blocking size.  e.g.
	
	tar cbf 1024 /dev/rmt4 .
	
	This allocates 1 Meg of memory  and dumps it to the tape drive.
A similar result can be obtained when reading from the drive (after
the memory is paged it.

	I wrote a small utility, "block" that reads from stdin and
dumps to stdout.  It serves to collect a bunch of data and stuffs it
to stdout.

	e.g. dump 0usf 3000 - /dev/em0h | block -b1024000 > /dev/rmt4.

	Using the dump without the block program takes in excess of
2 hours to write the disk to tape.  With block, it takes about 20 minutes.
Needless to say (so why am I saying it?) the system was very quiet while
this was in operation.

	As I avoid SysV like the plague, I can't say whether one can
obtain similar results with it.

	Finally, if you want to take a chance and execute a low-level SCSI
COPY command, you can usually back up an 85Mbyte drive in a few minutes.
The tape stops streaming only to change directions.

>Additionally, if your CPU board is very old, you may want (or need)
>to get it upgraded to the current revision level (which fixes some
>bugs that hinder I/O).  
>
>Call me when you get the upgraded goodies and we will discuss
>performance issues.

	I would be interested in the board improvements.  We have
several board sets obtained in late 85 to early 86 (I think).

	And while I am asking questions, is it possible to obtain
the Z-80 source for the ICM.  I am curious as to whether it would be possible to
make a couple of software/hardware improvements:

	1) Allow multiple initiators on the SCSI bus,
	2) Buffer tracks to/from the SCSI devices,
	3) Build a daughter board so that SIO's could be added
	   to the Z-80 section relieving the '016 from serial I/O tasks.
	4) Graphics via the Z-80.


-- 
Phone: (416)736-2100 x7765                               Tyler Ivanco
Institute for Space and Terrestrial Sciences  - Solar/Terrestrial Physics Lab
BITNET: fs300022@yusol         UUCP: ...uunet!mnetor!yunexus!gen1!tyler
        yfcs0027@yorkvm1                    ...utzoo!/