We have about 40 DB's blackening 40 web sites running on a single
SQL2k/Win2003 an A/P cluster. When I roll the cluster from one node to the
next I'm wondering exactly what sort of outage our clients would see. Since
the entire cluster rolls in under a minute would there just be a delay on
the web sites with data requests in response from the web/ODBC side or would
there be an ODBC failure. Also, with regards to active web sessions, would
clients mid transaction on the web pages need to restart their transaction
or would there be a short wait during the SQL roll and then they could
proceed with the transaction (or would they need to start all over again).
I guess I'm wondering if I need to add the 1 minute of roll time into our
annual downtime calculation if the clients see an application
failure/unavailability.

On the roll all client connections are lost and must be restarted. As for
what exactly happens, well that depends on the application. If the rows are
returned locally or if they are stored on the web server. And at what stage
in the process each client was in.

Bottom line, in most cases they either hit F5 (refresh) or never notice.

Cheers,

Rod

MVP - Windows Server - Clustering
http://www.nw-america.com - Clustering

"Mike B." <Autobahn97 (AT) hotmail (DOT) com> wrote

What the clients see or how it affects their transactions depends solely on
how the client app was written. It must be cluster aware. By that I mean
it must be able to detect a connection failure and reconnect. It must also
be able to resubmit the current transaction as it will be rolled back on the
server side when the cluster comes back up.

--
Andrew J. Kelly SQL MVP


"Mike B." <Autobahn97 (AT) hotmail (DOT) com> wrote

A cluster host transition is exactly like a SQL server stop-start. All
transactions are rolled forward or back at startup. The server is down
during the transition. The client application will see a connection timeout
or a query timeout or a broken connection. Whether the application traps
that or displays that to the end-user depends on the skill of the programmer
who wrote it.

Short answer, a cluster transition is downtime.

--
Geoff N. Hiten
Microsoft SQL Server MVP
Senior Database Administrator
Careerbuilder.com

I support the Professional Association for SQL Server
www.sqlpass.org

"Mike B." <Autobahn97 (AT) hotmail (DOT) com> wrote