SUMMARY: Memory File System

From: pmontr - Paul Montrose <pmontr_at_acxiom.com>
Date: Mon, 01 Jun 1998 15:02:17 -0500

The question was;
>
>
>We have a need to create a memory file system (mfs), on a DEC 8400 with 8Gb
>of memory running DU 4.0B with patch kit 7. Unfortunately, the only
>available documentation we have found are the man pages. Has anyone done
>this or have any information we can use?
>
I want to thank every for their answers, it seems they have found the
same thing we have, the man pages are the only documentation available.
To fill you in on a little more, we want to create a 4 Gb. memory files
system and wanted to know if there were any limitations or "watch outs,"
before we tried it. Also, we did contact DEC Gold support and they were
not able to furnish anymore documentation.

The following are the responses that we received;
>Here is an fstab entry:
>
>-s65536 /tmp mfs rw 1 0
>
>^^^^^^^ ^^^^
>size in mount point
>512K blocks
>(32MB)

-s204800 /tmp mfs rw 1 0

I put the preceeding in my /etc/fstab, do a 'mount -a' & have a 200MB
MFS /tmp file. The example in the man page ('man mfs') explains how to
directly create one.

The man pages on mfs should hold all the info that you require.

Eg: To create a 10Mb mfs on /tmp you should
        Place an entry in /etc/fstab like
                     -s20480 /tmp mfs rw 1 0
        Issue the relevant mount command ( ie # mount -a )

The mfs area will then be recreated at each boot time. Note that any
files in this area will , of course , disappear on rebooting etc.


 am writing to let you know that I posted a summary on this topic
earlier this month. I would send it to you, but I am not at my PC
(I do not keep mail on the server).

Easiest way to find it is to go to the net and do a search on the topic
and the word SUMMARY.


For the typical cases, the manual page is all you need. You need
to specify the size with the -s option and if you want the file
system to have private page/swap space there is an option for that.
My personal experience is that it is hard to create really large
memory file systems. I don't know if that is built-in limits or
process limits for the daemon that causes the file system to
exist. I was also doing my experiments on a relatively small
memory system. There may be a hard 2 GB limit for the memory
file system size. If it is documented anywhere, it would be
in the release notes where other size limits are documented.



mkdir /foo
mfs -s 81920 /foo

What do you want to do that's not in the man pages?
Received on Mon Jun 01 1998 - 22:03:44 NZST

This archive was generated by hypermail 2.4.0 : Wed Nov 08 2023 - 11:53:37 NZDT