To: "T64U Managers"
Many thanks to:
Vipin Gokhale <Vipin.Gokhale_at_oracle.com>
Nikola Milutinovic <Nikola.Milutinovic_at_ev.co.yu>
Who both said the same thing, more or less: "why do you need mfs to use
pipes?" For the one or two of you who shared my ignorance, I have included
part of Vipin's response below (my original question is at the bottom). The
bottom line is that my approach worked fine but was not necessary (or faster).
**** Vipin's response: ****
... pipes only occupy space in the file system for their directory
entry (which is a few KB in size in the worst of the cases). When pipe is opened
by
any process, read and write buffers are created in real memory, and data flows
through these memory buffers until the pipe is closed.
The only difference between a pipe created through mknod command and one created
through pipe syscall is that the one created through mknod is "visible" in the
file
system (e.g. you can do an ls on the directory, redirect input/output to it just
like a normal file from the shell command level etc). It doesn't matter what
file
system type the name/directory entry for this pipe exists in; read/write buffers
are always in real memory.
**** Original question ****
Hello all--
I think I have this right, but as I've never used mfs before,
I thought I'd better ask.
What I am trying to do is connect two mfs filesystems on two
separate systems using pipes, then use them as the source and
destination for an Oracle export/import. So on each system,
etc/fstab contains:
-s81920 /mtmp mfs rw 1 0
So about 40 mb of space on each side. Then I create pipes
with
mknod /mtmp/exp_pipe p (source)
mknod /mtmp/imp_pipe p (dest)
Then I do
1. Start import on destination with /mtmp/imp_pipe as input
2. connect pipes (from source) with
dd if=/mtmp/exp_pipe | rsh dest dd of=/mtmp/imp_pipe &
3. Start export on source with /mtmp/exp_pipe as output
4. Watch it scream.
I've tested this and it runs fast for small test runs, but..
a. Any issues with the size of the mfs partition? I assume the
space requirements for a pipe are small, but I have extra memory
so increasing the size is easy.
b. Any other comments/suggestions regarding dd, pipes, mfs etc.
that might help (or bite me)?
The underlying process has failed (for other reasons) twice now,
so I'm hoping for 'third time lucky' and a fast run tonight. All
suggestions, comments, etc. greatly appreciated.
--Russ
Received on Thu Jul 13 2000 - 20:13:51 NZST