milbery@rtech.rtech.com (Jim Milbery) (08/24/88)
I have worked with applications in the past that need to be "smarter" than the operating system. In particular, under VAX/VMS one can obtain software (best is EEC systems Turbodisk) than takes a portion of real memory and makes it look like a disk. users can then reference as a disk with directories, ala vma0:[dir]. 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
ji@read.columbia.edu (John Ioannidis) (08/25/88)
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