Changes between Version 4 and Version 5 of ServiceDeployment

Timestamp:

11/16/10 19:23:41 (14 years ago)

Author:

Dave Morris

Comment:

--

ServiceDeployment

@@ -91 +91 @@
 DNS information is cached, typically up to 3 hours, both at the client (desktop) and at the network level (e.g. the DNS service at UHL).
 
-This means that if we changed a DNS name for a live service at mid-day, there would be a period of time, approximately 12:00 - 15:00, where we could not predict whether a client would get an old (cached copy) or the new setting.
-
-If we relied on DNS aliases alone to migrate services between hosts, this could result in some users using the new service and others still using the old service.
-
-Best practice is to change a DNS alias overnight, when as few people as possible are using the service, allowing at least 6 hours for the DNS changes to propagate through the system before the majority of users start to use the system.
+This means that if we changed a DNS name for a live service at mid-day, there would be a period of several hours, 12:00 - 16:00, where it would be difficult to predict whether a client would get an old (cached copy) or the new setting. If we rely on DNS aliases alone to migrate services between hosts, this could result in some users being directed to the new service while others are still using the old service.
+
+Best practice would be to change a DNS alias for a service when as few people as possible are using the service, either overnight or at the weekend, allowing at least 6 hours for the DNS changes to propagate through the system before users sign in and start to use the system.
 
 == Virtual hosts ==