+h3. Slow migration on upgrade
+
+Important! This upgrade includes a database schema update changing the integer id column in each table from 32-bit to 64-bit. Because it touches every row in the table, on moderate to large sized installations *this may be very slow* (on the order of hours). Plan for the arvados-api-server package upgrade to take longer than usual.
+
+h3. Default request concurrency, new limit on log requests
+
+The configuration value @API.MaxConcurrentRequests@ (the number of concurrent requests that will be accepted by a single instance of arvados-controller) now has a default value of 64, instead of being unlimited.
+
+New configuration value @API.LogCreateRequestFraction@ (default 0.50) limits requests that post live container logs to the API server, to avoid situations where log messages crowd out other more important requests.
+
+h3. New limit on concurrent workflows
+
+New configuration options @CloudVMs.SupervisorFraction@ (default 0.30) limits the number of concurrent workflow supervisors, to avoid situations where too many workflow runners crowds out actual workers.
+
+h3. Default limit for cloud VM instances
+
+There is a new configuration entry @CloudVMs.MaxInstances@ (default 64) that limits the number of VMs the cloud dispatcher will run at a time. This may need to be adjusted to suit your anticipated workload.
+
+Using the obsolete configuration entry @MaxCloudVMs@, which was previously accepted in config files but not obeyed, will now result in a deprecation warning.
+
+h3. Default frequency for running keep-balance has changed
+
+The frequency that @keep-balance@ will run (@Collections.BalancePeriod@) has been changed from every 10 minutes to every 6 hours.
+