Conference ssdevo::hsz40_product

893.0. "Urgent help needed with volume shadowing and HSZ50" by ARAFAT::ASUNDQVIST (Crashes for nothing, and Dumps for free) Wed May 28 1997 10:12

Hi,

I have an urgent question involving OpenVMS Alpha V7.1, Host Based Volume
Shadowing and HSZ50. THis note is entered in the HSZ40 and the VMS conferences.

first, What We want to achieve:

2 systems in 2 separate computer rooms, clustered via fddi.
1 system is a 4100 with a dual redundant hsz50 and RS28D's
1 system is a DEC 3000 M800 with locally attached disks (RZ28D)
We want to shadow the disks between the two systems, as well as locally
(ie 4 shadowset members)

How we would like to do it: Use mirroring in the HSZ for the 4100, and
create a 3 member HBVS set with 1 member being the HSZ mirrorset, the 
other 2 two locally attached rz28's on the 3800.


To verify if it works, I set up 1 RZ28 on the local scsi-bus on the 4100 and
1 on the HSZ50. When I tried to do a mount/shadow=(disk-on-hsz, disk-on-local)
I got a SYSTEM-F-INCSHAMEM, incompatible shadow set member error message. This
is regardless of whether the disk on the HSZ50 is set to TRANSPORTABLE or not
(and inited with nosave on the hsz50 as well).

If I do the same thing with two RZ28D's on the HSZ50 it works ok, as long as
both have the same characteristics (ie transportable or not does not matter,
as long as both disks are created equal...)

it also works to do a HBVS set with 2 HSZ50 mirror sets.

What I finally found was that the same RZ28, when in the HSZ50 had
a different geometry than when on the local scsi bus (I physically moved the
disk). on the HSZ50 it had 85 sectors/track, 13 (I don't remember to number)
tracks per cylinder and 3000-something total cylinders. when put on the local
scsi, it gets 86 sectors/track 13 (the same number) tracks/cylinder) and a
smaller number of total cylinders. The only thing that is constant is the total
number of blocks.


This raises a couple of questions.

1) Have I missed something?

2) Should it work?

3) Where is all this documented?
   I have looked in the shadowing SPD, the Shadowing manuals and in various
   other places and have found nothing. Am I really the first to beat my
   head against this wall.

4) Is there an alternative way of doing it? 


If it is impossible to solve, could someone PLEASE explain why it can't be
done (I already know that an rz28d has different geometries depending on
where you put it, so that's not an explanation - I want to know why)

Some time ago the phrasing in the shadowing documentation was change to say 
that  disks with similar geometries can be shadowed. This has led me to  make
the assumption that a hsz mirrorset consisting of rz28d's and 2 RZ28D's locally
attached can indeed be shadowed using HBVS.

HELP

    There were some problems with the geometry on mirror sets with hsof
    5.0, you might want to go to 5.1 and see if that helps.
    

    I will try a bit of this.
    
    The answer to 1, 2, and 4 are Nope.
    on question #3, it shoud be documented in the OpenVMS release
    notes, stating that the drives are HBVS based on like geometries.
    So you can NOT shadow between alocal attached drive and one connected
    to an Array Controller. Also some controllers allocate different
    amounts of Metadata, and therefore you must ensure that the controller
    types are the same.
    
    Bert