![]() There were 3 copies in the main site and 3 copies in the Disaster Recovery site with one of those copies at each site being lagged. The customer had over 100 DB's, all with 6 copies each. There was a recent case that was the best example of Lag Replay Manager working in the real world. In the real world we don't always see Exchange setup according to our Preferred Architecture because of environment constraints or business requirements. By doing this it ensures that Exchange maintains at least 3 copies of each database. When there are fewer than three available healthy HA copies for more than 24 hoursĪ log "play down" essentially means that Replay Lag Manager is going to force that lagged database copy to catch up on all of the changes to make that copy current.When the lagged DB copy has physical corruption and needs to be page patched.When a low disk space threshold (10,000MB) is reached.disk IO) into consideration before invoking the lagged copy. Ross Smith's post does a wonderful job of explaining them and how Exchange will take other factors (i.e. The Replay Lag Manager will constantly watch for any of the three things to happen to the copies of DB1. Even though we're showing it in a secondary site, it can exist in any site where a node in the same DAG resides. The PA uses 4 database copies like the following:Īs you can see the 4th copy is a lagged copy. To understand what it is let's look at the Preferred Architecture (PA) in regards to a database layout. The Replay Lag Manager was first introduced in Exchange 2013 and is actually enabled by default beginning with Exchange 2016 CU1. To further explain, a lagged database copy is a database that Exchange delays committing changes to for a specified period of time. In a nutshell, Replay Lag Manager provides higher availability for Exchange through the automatic invocation of a lagged database copy. I wanted to cover a real world scenario I had dealt with recently with a customer that I believe will clarify some things. We've seen a few support cases that seemed to have been opened out of the misunderstanding of what the Replay Lag Manager is doing. It's a great feature that's somewhat underappreciated. In a previous blog post Ross Smith IV had explained what the Replay Lag Manager is and what it does.
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