How to upgrade SharePoint from one version to another version without any downtime

Hi All,


Today I want to share about how to upgrade SharePoint farm from one version to another version without downtime. This is the best approach when we are working on business application where we can not take down time or we can say where will have impact on business if we take down time like banking applications.


Here we need to set up Disaster Recovery farm has been set up with SQL Server AlwaysOn.


Now follow the below steps to upgrade SharePoint farm.


Step 1: Leave users going to primary site and meanwhile patch disaster-recovery/secondary site.

1. Ddetach the content database from the DR farm 1st, as PSConfig will fail to finish the upgrade while these databases are still connected to the farm & in read-only mode (as the DR site will still be the secondary replica in SQL Server).
2. syntax: Dismount-SPContentDatabase <ContentDB GUID>
3. PSConfig will update all databases except the content databases.
4. Re-attach the content databases, and maybe even run an incremental crawl if you want your indexes to include updates since the content DBs went offline.
5. Syntax: Mount-SPContentDatabase <databasename> -DatabaseServer <db_server> -WebApplication <webapplication_URL>
    
6. Verify SharePoint is happily working again on the DR site – check logs, site-access etc

Step 2: Switch users to the upgraded DR site + failover SQL Server to use the secondary node as the new primary. SharePoint on the DR site will use the content-databases in compatibility mode but with read/write access.

There will be a service interruption while this simultaneous databases + user switchover happens. Might want to make the switch at night, for example.

Step 3: Patch primary farm, now that users are on the DR site.

Once the normal farm is verified as healthy again, failover users there again if you so wish.

Both farms are now upgraded with content-databases in compatibility mode.

Step 4: On the farm with read/write access to the content-databases, finish the upgrade with Upgrade-SPContentDatabase. This may cause some read-only access while the upgrade is happening but it’ll be much less read-only time than the safer method below.

This is the preferred way: read/write functionality still works for users almost without interruption. This full functionality is available much more than was previously possible as AlwaysOn lets us switch primary servers back & forth trivially.


Shortly: upgrade DR farm 1^st (with content DBs disconnected) while users still use the primary farm. Then reconnect content DBs, switch users + content DBs at the same time to DR farm once the DR farm is upgraded. Once everyone’s on the DR farm, upgrade primary farm. Finally upgrade content-databases in PowerShell.


Reference