IBM TSM : my exchange database backups are twice the total size of my databases

Hello experts,

I am having an issue with my exchange backup.

I use tdp for exchange    . My exchange DAG is a cluster of  2 mbx servers. The total of the databases are supposed to be less than 5 terrabytes.

When Watching my tsm reports, I have noticed that the size of my DAG backups is around 9 terrabytes wile I do daily incremental backups and I only keep one version of each backups!

I also noticed that the preferDAGpassive option is set to false? Do I backup twice the dabases?? Whats the best practice, please I am lost. whats the real meaning of preferdagpassive?

preferdagpassive
Williams225System AdministatorAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

x
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Will SzymkowskiSenior Solution ArchitectCommented:
Exchange as a whole it is always recommended to backup the passive node while doing backups for DAG environments (if your backup software supports it). Each backup method can slightly differ based on the vendor that you are using and the technologies that they use to backup the software.

However i am not familiar with your backup software but rule of thumb is backup the passive node. See the below link for additional detail.

https://technet.microsoft.com/en-us/library/dd876874.aspx

Will.
0
Williams225System AdministatorAuthor Commented:
Ok you are right, I have just  noticed the preferdag passive is set to true in my backup script.

But What I don't understand is the fact that  the size of my exchange backup is twice the size of the exchange databases size while i only keep one active version of all exchange backups.
0
MASEE Solution Guide - Technical Dept HeadCommented:
This could be because of exchange database's de-duplication feature. A message sent to multiple users will be stored once and each user will have a pointer to it. When a brick-level backup is performed this de-duplication is undone, and each mailbox is backed up separately.
Please check this as well
http://serverfault.com/questions/144739/exchange-backup-size-larger-then-file-size
0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Storage Software

From novice to tech pro — start learning today.