DecSafe shared file domain: Am I in the right track ?

From: Guy Dallaire <dallaire_at_total.net>
Date: Fri, 20 Sep 1996 23:31:43 -0400

Hi,

I want to have various advfs file domains shared (not at the same time)
between 2 alpha servers 2100 running DU 3.2D and DecSafe. I know that
DecSafe 1.3 does not have a distributed lock manager and I do NOT plan to
use a shared disk with 2 machines at the same time. All I want is that, in
the event of a crash, the surviving host mounts the shared disk and make it
available or run critical apps and be able to use data on that disk (An
Oracle database, information system programs and Polycenter Scheduler). I
use HSZ40 and my harware is correctly configured for DecSafe.

I tried something that seems to work but I wanna make sure that I used the
correct procedure and answer some questions along the way.

1) On the first machine, I created a file domain (testdmn) and a fileset
(testfs). I then mounted the fileset under /test, populated it with data
and unmounted it.

        mkdir /test
        mkfdmn /dev/rzb11c testdmn
      mkfset testdmn testfs (I dont remember the exact syntax)
        mount -t advfs testdmn#testfs /test
      ...create some files under /test
      umount /test

2) I then logged on the second system and did the following:

        mkdir /test
Q1-> mkfdmn /dev/rzb11c testdmn
Q2-> mkfset testdmn testfs (I dont remember the exact syntax)
        mount -t advfs testdmn#testfs /test

        play with the files created in step 1 and they seemed OK.

It looks like the mkfdmn command (Q1) doesn't destroy the existing
filedomain on the disk. I know that it creates a directory structure
somewhere but does it write something on the disk and risk destroying the
data ? Same thing for Q2.

Is that procedure OK ? I see no way of _easily_ being able to transfer the
control of the shared device to the other machine other than recreating the
exact same mount points, domain names, etc... Is this true ? If not, what
is the proper way to do this ?

Please forgive my bad english, I'm french speaking.

                                                        TIA !

P.S.: I would also like to know what happens if by error, both machines try
to acces the same shared disk. For example, if I forget to umnount it on
the 1st machine and mount it on the second one. Will that destroy data or
will the system only give me an error message stating that the device is in
use without messing things up ?
Received on Sat Sep 21 1996 - 05:53:38 NZST

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