From:	MERC::"uunet!CRVAX.SRI.COM!RELAY-INFO-VAX" 23-APR-1992 22:25:37.02
To:	info-vax@kl.sri.com
CC:	
Subj:	Re: LAVCs, quorum etc...

In article <1992Apr23.074915.5589@cco.caltech.edu>, carl@SOL1.GPS.CALTECH.EDU (Carl J Lydick) writes:
>In article <901@se.alcbel.be>, mvbr@se.alcbel.be (Marc Verbruggen) writes:
>>
>>--
>>We have an LAVC with two bootmembers, connected by a DSSI, to which 4 disks 
>>are attached, including the system disk ($1$DIA0).
>>On those bootmembers following SYSGEN parameters apply :
>>
>>             VOTES = 1
>>    EXPECTED_VOTES = 3
>>         QDSKVOTES = 1
>>       DISK_QUORUM = DIA0
>>
>>Satellites have VOTES = 0 and EXPECTED_VOTES= 3
>>Despite these, in my opinion, correct settings, the second bootmember loooses
>>quorum and hangs, when the other bootmember is out of service. 
>>This, I do not understand.
>
>Well, let's see.  If you've got both bootmembers and the quorum disk on-line,
>then you've got three votes.  One bootmember goes down, and now you've only got
>two.  Set your EXPECTED_VOTES to 2.
>--------------------------------------------------------------------------------
>Carl J Lydick | INTERnet: CARL@SOL1.GPS.CALTECH.EDU | NSI/HEPnet: SOL1::CARL
>

   Hmmm.  I don't think so here.  I have a 6420 and a 4200 clustered via
   DSSI, with an RF72 as the quorum disk, in much the situation described
   above, except:

        6420                       4200           
      -------------              -----------------
      VOTES = 2                  VOTES = 1        
      QDSKVOTES = 2              QDSKVOTES = 2
      DISK_QUORUM = "$5$DIA0:"   DISK_QUORUM = "$5$DIA0:"
      EXPECTED_VOTES = 5         EXPECTED_VOTES = 5

   Quorum is then calculated from Expected_Votes: (5+1)/2 = 3, so either
   system can continue without the other, as long as it has "local" access
   to the disk.  (This has worked in the past, too!)

   I suspect that the DISK_QUORUM field is set incorrectly (i.e., without
   the ALLOCLASS value), and the disk's votes are not getting counted.
   You can see for sure by doing the following:

        $ SHOW CLUSTER/CONTINUOUS
        Command > ADD CLUSTER

   This will show the cluster status, including the current quorum 
   (CL_QUORUM), the current number of votes (CL_VOTES), and whether there
   is a quorum disk contributing (QF_VOTE).

                                                - Tom
--
Thomas H. Hopson                                mgrthh@rosevc.rose-hulman.edu
VMS Manager                                     mgrthh@rhit.bitnet
Rose-Hulman Insitute of Technology              thomas.hopson@rose-hulman.edu
Terre Haute, Indiana