Thanks to the following:
jgmicon_at_sandia.gov
alan_at_nabeth.cxo.dec.com
sanghvi_at_proto.wilm.ge.com
baranowskit_at_gdynia_at_genesis.prokom.gdynia.pl
iwm_at_uvo.dec.com
cherkus_at_UniMaster.COM
Zieglerr_at_novachem.com
john_at_iastate.edu
chandrasek_at_odixie.ENET.dec.com
>From Alan:
----------
DECsafe is software that allows setting up two (maybe
more) systems to act as fail-over servers for one
another. On a service by service basis (NFS, etc)
if one detects the other down, it will become that
other system.
TruCluster as it exists today is the first step in
offering full VMScluster like functionality on Digital
UNIX. I think the first stage allows having special
device files on each system that are the devices on all
the other systems. This allows the systems equal access
to each other's devices and shared devices. The danger
of this shared access is that few components of the system
do the locking necessary to maintain consistency. I think
another part of the current offering is a lock manager that
cooperating processes can use to do the necessary locking.
In order to provide the necessary memory to memory bandwidth
the systems use Memory Channel devices which are PCI devices
that can provide DMA access between the two system's memory.
Future stages of the product will probably include a multi-
host file system that contains all the locking needed so that
two or more systems can have direct access to the same set of
file systems. NFS uses server processes that provide the
context for the underlying I/O. Using Memory Channel each
system can have equal access directly to the file systems.
At some point they're bound to support a cluster hostname,
which simplifies failover service, since a group of systems
all have the same outside name. Access to the cluster name
will be load balanced among all the systems in the cluster.
When all the parts are in place, I'd expect TruCluster to
mostly replace DECsafe. But, the hardware needed to run a
cluster at speed is relatively expensive and there may still
be a need for the lower cost failover that DECsafe provides
today.
Fair warning... It was a couple of years ago that first saw
anthing about TruClusters and I've forgotten most of the details.
If you look around on our Web server (www.digital.com) you may
find pointers to white papers that will describe each in some
detail.
>From Tomasz:
-----------
Hello.
There is web page about TruCluster Soluitions
(for text version address)
http://www.unix.digital.com/bin/textit/cluster/index.html
There are doc's in PDF, Postscript, HTML and text format.
Generally DECsafe is functionally subset of TruCluster.
Have nice day ;-)
Regards,
>From Dave:
---------
There is now a family of products called TruClusters.
One element, called the TruCluster Available Server Software
product, is what used to be called DecSafe and/or ASE.
The other element, called TruCluster Production Server Software,
is a newer product that uses parts of ASE and new software such
as a distributed lock manager, and new hardware such as memory
channel, to provide a high performance, high availability
environment for databases such as Oracle Parallel Server.
So, when you say TruClusters you need to understand that
you are really talking about more than one thing.
Whether you use Availability Server or Production Server is
based on your intended use.
http://www.unix.digital.com/cluster/index.html
for more info.
>From John:
----------
With DECsafe a particular service (examples: Oracle, NFS, mail, etc)
runs on 1 machine. Should that machine go kaput for some reason,
the service is moved (more or less transparently) to another machine.
The disks of these machines are connected via shared SCSI bus(es),
but only 1 machine has any particular service's disks mounted at
any given time. A service also has an IP address (distinct from
the IP address(es) of the machines them self). This address also
moves with the service.
In TruCluster a service runs on multiple machines at once
(example: Oracle Parallel Server) and the disks can be
accessed via multiple systems at the same time (the
"distributed raw disk" system).
TruCluster includes a new piece of nifty high-speed interconnect
hardware called the Memory Channel.
TruCluster is very similar to VAXcluster, (and going to
get closer in the future, I assume) if you know VAXcluster.
}Is TruClusters a replacement for DecSafe?
Not exactly. It is a significant extension of function.
I presume DECsafe will remain a product option for those
who don't need/want the functionality/expense/complexity
of TruCluster.
}Do they perform the same function?
No (see above).
}If I'm currently running DecSafe should be be moving to TruClusters?
Only you can answer that. We are staying with DECsafe on
our "high-availability" Oracle server pair at present.
At least in part because the memory channel hardware is
not "qualified" for our 1000A servers (last I knew).
And partially because we don't need the features or
complexity at present.
>From Kris:
----------
TruCluster is the program name for Digital's family of UNIX cluster
offerings.
TruCluster Production Server allows use of a distributed database,
such as Oracle Parallel Server, so that multiple system can access
the database concurrently, and the failure of a single system
still allows access to the database. The Production Server supports
Memory Channel hardware. In the future, Informix's XPS will also
be supported.
TruCluster Available Server (aka DECsafe) is an environment for providing
a quick recovery, failover (high availability) environment for many
UNIX applications. The functionality of the Available Server is
included in the Production Server.
Till UNIX V3.2D there was only DECsafe available, UNIX V3.2E provided
TruCluster Production Server capabilities. If you use
DECsafe today, there may be no need to go to TruCluster Production
Server, but it all depends on your situation, what application you
are using, and whether you really desire to go to TruCluster Production
Server.
Look at
http://www.unix.digital.com/cluster/index.html for more
information. You can get a white paper on TruCluster, as well as
Software Production Descriptions (SPDs).
Regards, Kris.
Original Question
-----------------
Hello,
Can someone explain the difference between DecSafe and
TruClusters?
Is TruClusters a replacement for DecSafe?
Do they perform the same function?
If I'm currently running DecSafe should be be moving
to TruClusters?
Thanks
Les Mayeda
Cedars-Sinai Medical Center
mayeda_at_csmc.edu
Received on Fri Dec 20 1996 - 03:35:24 NZDT