Path: utzoo!attcan!uunet!peregrine!elroy!ames!ucsd!rutgers!columbia!read.columbia.edu!ji
From: ji@read.columbia.edu (John Ioannidis)
Newsgroups: comp.sys.hp
Subject: Re: HP unix Ram-drivers, anybody out there ?
Message-ID: <5846@columbia.edu>
Date: 24 Aug 88 19:56:44 GMT
References: <2396@rtech.rtech.com>
Sender: news@columbia.edu
Reply-To: ji@read.UUCP (John Ioannidis)
Organization: Columbia University Department of Computer Science
Lines: 40

In article <2396@rtech.rtech.com> milbery@rtech.UUCP (Jim Milbery) writes:
>
>I am working on an hp 9000/350 with hp/ux, and am wondering if there exists
>some public domain or commerical software available under unix to do the
>same.
>
>jimmilbery 617-272-5060 @ RT

HP-UX 6.0.1 and higher  have support for RAM drivers. Here's an excerpt from
/etc/rc on my home machine (an hp9000/350 with 8M of ram)

# @(#) $Revision: 56.16 $     

# Create and mount the 6.0 ramdisc on /tmp:
# Make sure the size specified in the minor number matches the newfs size.
# The maximum size possible is 4meg.
#	rm -rf /dev/dsk/ram /dev/rdsk/ram
#	/etc/mknod /dev/dsk/ram4  b  4 0x003fff
#	/etc/mknod /dev/rdsk/ram4 c 20 0x003fff
#	/etc/newfs -v -n -s 4095 -m 0 -i 32768 /dev/rdsk/ram4 hp7945_noswap
#	if /etc/mount /dev/dsk/ram4 /tmp
#	then
#		chmod 777 /tmp
#		rm -rf /tmp/lost+found
#		echo ramdisc mounted on /tmp
#	fi

Since I only have 8M of ram, I can't afford to use a ramdisk. Besides, 
I took some rough measurements once doing heavy C compilations, and
it didn't matter whether I had a ramdisk or not. (the various passes of
the C compiler write stuff in /tmp, only to be read by the next pass. 
Writes are not synchronous, and the blocks are still in the buffers when
the next pass reads them)

Allocating a large ram disk is not always a good idea -- you'll end up
paging more often. 

Hope this helps

/ji