Hi All,
This list rocks!
Thanks to:
alan at something dot cpqcorp dot net
Dr. Thomas P. Blinn
Bryan LaVelle
Alan Davis
Jim Kurtenbach
Joerg Bruehe
Lucien HERCAUD
Michael Huntington
Apologies to anyone I might have missed.
The original question(s):
I'd like to configure one SCSI bus that has the following three bus
devices on it:
1) Compaq DS20 running Tru64 UNIX with SCSI address x
2) Compaq DS20 running Tru64 UNIX with SCSI address y
3) generic 3rd-party disk storage subsystem with SCSI address z
and mount(8) the disk device in (3), above, read/write on both DS20's.
Is this possible?
Have you done it? If so, what's the recipe for doing so?
The answer(s):
Yes,
Yes, and,
Use TruCluster that became available as of V5.0A. On V5.1 the two
systems must have Memory Channel as their private communcation path,
but in V5.1A, a private LAN can be used. Use only supported I/O
subsystems.
[Plain ol' mount(8) without clustering] Won't work. Period. Forget
about it. If you really want to get something along those lines
working, you need the right choice of SCSI adapters, you need
TruCluster software, you need exactly the right termination scheme,
and even then, it's often "iffy". You are MUCH better off not even
trying to do this yourself.
The ONLY supported way to do this is to run a cluster. Anything else
and you will absolutely trash the data on that disk.
This is not supported in any configuration except TruClusters.
If the third party storage implements something like selective
storage presentation and it works, you could use a SCSI hub to
isolate the systems. This type of configuration is supported on the
HSZ* series of storage. The key here is that only one system can
mount each device, but the storage presents multiple devices each to
an individual node. There is no "dual mount" capability. If you want
both systems to access the same disk you have to use Trucluster or
mount it on one and export an nfs filesystem to mount on the other.
It's electrically possible to connect it as you describe, but the
certainty of data corruption and crashing one or both systems is
100%.
Yes, you can probably do it. The caveat that I worry about is
file/directory locking as each ds20 has no idea whether a
file/directory is being written to by the other.
However, you could modify the partition maps on that drive (on each
machine) so that one machine uses the first "half" of the disk and
the second machine uses the second "half".
Set the id of the scsi controller to 6 on one of the machines (>>>set
pka0_host_id 6) and seven on the other. Set the drive with a jumper
as id 0-5 and it should work.
I can imagine two different scenatios:
a) Both machines mount the same filesystem on the shared disk.
As any Unix machine does keep a cache of file system pages, a
shared mount would require them to synchronize these caches.
There may be a Tru64 option (coming from some cluster stuff) to do
that, but I have no knowledge in this area.
If you do not get them to synchronize, this will ruin the shared
file system.
b) Both machines mount different file systems, residing in
different partitions.
As long as the partition table remains unchanged, I expect this to
work - but I never tried.
If you pursue this any further, you should clarify which way you are
looking into.
The most valid answer is : YOU NEED THE CLUSTER SOFTWARE on Tru64
5.1* in order to do this (ie. to allow you to share R/W the same disk
device as a raw device or as a mounted fileset).
According to special cases (special usage), there MAY be other
answers: 1. You can always share in READ ONLY MODE for the raw
device or for a readonly mounted UFS filesystem. (AdvFS does not know
what readonly mount is !) 2. You can READ/WRITE use a partition on
machine A (raw of any fileset usage UFS or AdvFS) and READ/WRITE
another disk partition (raw of any fileset usage UFS or AdvFS) on
machine B (but do not attempt to modify the disk partition table on
any of the 2 machines !!!) 3. You can share the same partition of the
disk (raw) in READ/WRITE mode if you manage to solve the interlock
algorithm within your application running as a whole on the 2
machines (this means a lock manager !!!)
Thanks All!
-- Ed
Received on Wed Mar 06 2002 - 02:02:03 NZDT