Failsafe errors simply report that the SentryOne Monitoring service was not able to synchronize data for some reason. They are to be expected when either the SentryOne (SQLSentry) database server or the target server are under heavy load so the Monitoring Service can't connect and do its work. Here are some possible causes:
1) Optimization tasks on the SentryOne database such as integrity checks or index rebuilds. 2) Backups of the SentryOne database. 3) Network backups to/from a watched server or the SentryOne database server. 4) Other activities which cause very high disk, CPU, or network utilization on either the SentryOne database or watched server. 5)TCP Offloading is enabled: http://blogs.msdn.com/b/psssql/archive/2010/02/21/tcp-offloading-again.aspx.
If you see a pattern in the timing of the errors, there is a good chance it's one of the issues mentioned above and is happening on a scheduled basis. If so, you can use any combination of the maintenance window features in SQL Sentry to mask any failsafe alerts during a specified window:
1) Maintenance window for the SentryOne database (Configuration -> Global Settings -> Alerting Tab -> Maintenance Window Section) or (Monitoring Service -> Settings -> Maintenance Window Tab) for version 10 or lower.
2) Maintenance window for computers, set in the Settings pane -> Computer Settings -> Maintenance Window section. Setting a window at the computer level automatically applies to all connections for a computer, unless overridden at the connection-level as covered in #3. The recommendation is to start at the global level (All Targets node/Shared Groups node in version 10) first, which will make it the default for all computers and watched connections. You can then easily override the window for individual computers as needed by selecting a computer in the Navigator and setting "Inherit From Parent" to False.
3) Maintenance window for watched connections, set in the Settings pane -> Settings -> Connection -> Maintenance Window section. The recommendation is to start at the global level (All Targets node/Shared Groups node in version 10) first, which will make it the default for all connections. You should go through each connection type (SQL Server, Oracle, Task Scheduler, etc.) and set it for each. You can then easily override the window for individual connections as needed by selecting a connection in the Navigator and setting "Inherit From Parent" to False.