Solved

Exchange lagged database copy

Posted on 2014-07-28
4
347 Views
Last Modified: 2014-07-29
I have done some readings on Microsoft website about Lagged database copy, but still not clear.
I want to know what s the purpose of it. I know the lagging is applied only on the passive database copy not on the active and the lagging delays the replay of the logs for a specified time.

However I believe if something happen to active copy, the passive will become the active and the logs will be replayed...anyway

in Some articles, they say that the lagging comes in handy when the active database is corrupted, and when the corrupted data is copied to the passive copy, it will not replayed until it reach the specified time in Lagging...if we realize that there is corruption within that time frame, then we can just initiate the replay of the logs generated before the corruption happened, and delete the logs generated after the corruption happened. .....Too complicated...

I could be wrong...I need Exchange expert to shade some lights on this topic.

Thanks
0
Comment
Question by:jskfan
  • 2
  • 2
4 Comments
 
LVL 63

Assisted Solution

by:Simon Butler (Sembee)
Simon Butler (Sembee) earned 500 total points
ID: 40226358
The articles you have read about database corruption being a reason for using a lagged copy are wrong.
Database corruption cannot replicate across a DAG, because the replication happens via the logs, not the actual database file.

The only reason I can see for having a lagged copy is to allow an error by a user or admin to be caught.
For example an admin is doing a mailbox export and gets it wrong and deletes a lot of content. A user deletes a lot of content and there are no backups etc.

However, I have never deployed a lagged copy of the Exchange databases. Most clients and implementations want a live copy, so if the active server fails all of the content is located on the passive server and nothing can be lost.
With deleted item retention on the database, the reason for having the lagged copy pretty much goes away.

The only other time I can imagine having a lagged copy would be to delay the replication because the link is so slow or heavily utilised. Put a lag of 8-10 hours on the database and move content replication will happen out of business hours. Pretty poor reason though, and not something I have ever done or even suggested to a client.

Simon.
0
 

Author Comment

by:jskfan
ID: 40226797
Do not you think if the Active Database gets corrupted at certain point in time , it will still replicate the corrupted logs to the passive database copy.

 Then if they get replayed right away on the passive copy , then both Active and passive copy will be corrupt
0
 
LVL 63

Accepted Solution

by:
Simon Butler (Sembee) earned 500 total points
ID: 40226843
If the active database gets corrupted then that corruption isn't going to replicate because the second copy is created using the transaction logs.
In effect, database corruption isn't an issue, because if you get a corrupt database then simply drop the copy that is corrupt and reseed. Corruption cannot move between the database copies.

Simon.
0
 

Author Closing Comment

by:jskfan
ID: 40228247
Thank you!
0

Featured Post

Want to promote your upcoming event?

Attending an event? Speaking at a conference? Or exhibiting at a trade show? Easily inform your contacts by using a promotional banner in your email signature. This will ensure your organization’s most important contacts are in the know.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Marketers need statistics and metrics like everybody else needs oxygen. In this article we explain how to enable marketing campaign statistics for Microsoft Exchange mail.
Scam emails are a huge burden for many businesses. Spotting one is not always easy. Follow our tips to identify if an email you receive is a scam.
In this video we show how to create a Shared Mailbox in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center. Navigate to the Recipients >> Sha…
This video shows how to remove a single email address from the Outlook 2010 Auto Suggestion memory. NOTE: For Outlook 2016 and 2013 perform the exact same steps. Open a new email: Click the New email button in Outlook. Start typing the address: …

947 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

22 Experts available now in Live!

Get 1:1 Help Now