October 29, 2015 at 3:07 pm
Hi Expert,
I need a advice.
1. Once fail over to secondary replica, what will happen to connected session in primary node? can the session fail over to secondary seamlessly or need to re-login. what happen committed transactions which has not write to disk.
2. Assume I have always on cluster with three nodes, if primary fails, how second node make write/ read mode.
3. after fail over done to 2nd secondary node what mode in production(readonly or read write).
4. how to rollback to production primary ,will change data in secondary will get updated in primary
regards
ud
October 30, 2015 at 3:53 am
Hi,
Current sessions on the failing node will be lost. You have to add some logic in your application to reconnect.
October 30, 2015 at 4:02 am
Always On Failover Cluster
or
Always On Availability Groups on a Always On Failover Cluster
Always On is just a marketing term, generally dropped as it means nothing really, so generally detail if its an Availability Group setup or just a plain cluster setup
Linking to Perry's stairway on the topic
October 30, 2015 at 4:25 am
udara0306 (10/29/2015)
Hi Expert,I need a advice.
1. Once fail over to secondary replica, what will happen to connected session in primary node? can the session fail over to secondary seamlessly or need to re-login. what happen committed transactions which has not write to disk.
Sessions will be disconnected, if you're using a listener the connections will be able to reconnect once this is started.
All transactions are hardened to disk in the transaction log, dirty buffers are written in the background. Even so, a hardened record of any change exists.
udara0306 (10/29/2015)
2. Assume I have always on cluster with three nodes, if primary fails, how second node make write/ read mode.
Please supply more detail, are these sessions synchronous or asynchronous? Do you have automatic failover configured?
udara0306 (10/29/2015)
3. after fail over done to 2nd secondary node what mode in production(readonly or read write).
If you failover your alwayson group to a secondary node this then becomes the read\write primary
udara0306 (10/29/2015)
4. how to rollback to production primary ,will change data in secondary will get updated in primaryregards
ud
If you wish to fail back to the previous primary another manual failover would be required, as long as the databases are synchronised the data will be safe
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"Ya can't make an omelette without breaking just a few eggs" 😉
October 31, 2015 at 2:37 am
Hi,
My always on cluster 2 replica with sync mode and DR one with Async mode.
regards
ud
November 2, 2015 at 3:45 am
udara0306 (10/31/2015)
Hi,My always on cluster 2 replica with sync mode and DR one with Async mode.
regards
ud
If you have 2 replicas configured for synch mode and auto failover the transition will be automatic, hence the term auto failover. The secondary will become the new primary and the primary will become a secondary, this is based on the policy set when creating the AG
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"Ya can't make an omelette without breaking just a few eggs" 😉
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