MILLS%OSU-20@OHIO-STATE.ARPA (05/29/86)
DEC's new uVAX ethernet clustering product is not original to
DEC. Here at the Ohio State University, we have been clustering
VAXes (mostly 11/750's) on an ethernet-based cluster since last
September. This method of clustering was developed in-house for
a major third-party disk company, who now markets it.
The exact same product will work on uVAXes as well as UNIBUS
VAXes, but DEC's cluster modules are not included in the uVMS
distribution. Since DEC's cluster modules are licensed software,
it appears to be illegal to have them on a uVAX to run the
ethernet clustering product on uVAXes.
The ethernet cluster is a reliable, low cost alternative to DEC's
expensive CI cluster. As expected, the performance is slightly
lower than found in the CI hardware, but the price per feature is
much better.
Virtually all of the DEC CI-based cluster's features are present
in this implementation. All of the DEC utilities, such as SHOW
CLUSTER, XQP, MSCP, and operator functions, etc, work with no
modifications or alterations to the software or the functionality
of the features with the following exceptions:
1) DECnet's CNDRIVER will not use the ethernet-based cluster.
DECnet must run parallel on the DEUNA.
2) There is not an ethernet equivalent to the HSC controller.
There are also aspects of the ethernet cluster which cause some
degredation in performance of the cluster. These include:
1) The cluster lock manager is slower, primarily because the
speed of the ethernet media (10 Mb) is much slower than the
speed of the CI media (70 or 140 Mb). The actual speed of
the cluster lock manager is approximately one-third of
of the CI implementation (150/sec on CI, 50/sec on
ethernet)
2) MSCP-served disks cause greater overhead than in the CI
cluster due to some memory-to-memory transfers that are
necessitated by the ethernet driver. Particularly, the
/HIGHWATER feature (zeroing files when they are allocated)
causes a noticable lag for large files through the ethernet
cluster.
The ethernet cluster software makes use of the XEDRIVER's FFI
interface, thereby allowing sharing of the DEUNA/DELUA by DECnet,
LAT, and the cluster software. Other ethernet interface boards
(besides the DEUNA/DELUA) are currently not supported.
Several of the cluster sysgen parameter's functionality has been
redefined to control the ethernet cluster. While the ethernet
clustering product has not been tested with more than about six
or eight members here at the Ohio State University, it is
believed that there is no conceptual problem in having more than
sixteen nodes in one ethernet-based cluster.
At the Ohio State University, we make use of the ethernet-based
cluster at several VAX sites, and depend upon it to provide
reliable computing service to faculty, staff, and students.
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