Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!sun-barr!texsun!pitstop!sundc!seismo!uunet!mcvax!cernvax!achille
From: achille@cernvax.UUCP (achille)
Newsgroups: comp.sys.apollo
Subject: Re: TAR (SR9.X), cartridges
Message-ID: <998@cernvax.UUCP>
Date: 10 May 89 10:51:50 GMT
References: <8905090651.AA01180@icaen.uiowa.edu>
Reply-To: achille@cernvax.UUCP ()
Organization: CERN European Laboratory for Particle Physics, CH-1211 Geneva, Switzerland
Lines: 32

In article <8905090651.AA01180@icaen.uiowa.edu> dbfunk@ICAEN.UIOWA.EDU (David B. Funk) writes:
>Utilities like /com/wbak, /com/rbak, & /systest/ssr_util/cptape do not
>use streams I/O to get to ctape, they use an unreleased interface, the "ct_$"
>calls. Their performance is OK, about 1 Megabyte/minute. Utilities like
>/com/rwmt & tar use the streams I/O system, and their performance is
>hurting, about 0.1 Megabytes/minute.
>..........
>Dave Funk

Just a couple of info to put things in the right place:

	1) wbak, rbak, rwmt ALL use tfp_$ calls to access the tape
	or cartridge or floppy.
	The only difference here is that w/rbak use tfp_$block_list_io
	(sp?) to perform IO in BIG chunks, rwmt uses record IO and so
	is pretty slow on ct as the max record length there is 512 bytes
	(as opposed to magtape where I think is 16K and rwmt performs
	decently on them).
	2) cptape uses ct_$.

As a side note, performance via C I/O on exabytes (under sr9.7) is not that bad
when compared to w/rbak.
When I am at exabyte, I posted some time ago a request for help about
write errors on our (Workstation Solution) exabyte.
As it comes out, the power supply they use in the older units (the new
ones they ship have a different one) has problems on 220V.
The ripple on the +12V gets up to 1.5V (max. should be 150mV).

Hope this helps,

Achille Petrilli
Cray & PWS operations