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Offline defrag of Exchange 2010 DAG DB

Please do not just tell me I don't ever need to defrag, thanks.

I am having a problem with my email archiving solution at the moment which should be resolved shortly. This has lead to my two DAG'd DBs getting dangerously close to filling their partitions.

I have installed a new partition on all the DAG servers and I will be creating a third DB soon to spread the mailboxes out.

Once the archiving solution comes back and mailboxes are shrunk I want to know how much free space there actually is on my two original partitions.  So while I have this empty third partition before I create the third DB, I have the chance to either (A) create the third DB and shuffle all mailboxes to it from each database one at a time recreating the other two databases in the process or (B) use the space to offline defrag the other two DBs.

The reason I don't want to do (A) is that one of the nodes of the DAG is in another office and it would take a looooong time for it to catch up with all the moving around of mailboxes.

So I would prefer to do the defrags, however I can't find the procedure to do this with regards to DBs in a DAG. Every post on t'interweb is just answered with you don't need to do it.

I know the DB files won't grow while there is space 'in side' them but I want to know exactly how much free space I have so that I can effectively balance the final 3 DBs.

I could in theory bring the third EX server back to this office for the dance of the mailboxes but that would be a pain and only worth it is the defrag process is extremely painful or dangerous.

Cheers,
Sam.
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Sam_Rendell
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Sam_Rendell
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endital1097Commented:
you would need to first suspend all database copies
then dismount the active database
run the defrag against all copies
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Sam_RendellAuthor Commented:
Ok thanks, would you say this is the sensible option over moving the third EX box back to head office and then moving/recreating DBs?
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endital1097Commented:
if you wanted that third to be a DR server, no
you just need to make sure that in the main site you have a majority so that if you lose the WAN your main site will stay online
the remote site would lose majority and go offline
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endital1097Commented:
sorry, misunderstood the question

yes, depending on the size you don't want to generate a lot of wan traffic
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endital1097Commented:
i also should have added once the defrags were complete on all you would resume the database copy, but you probably already knew that
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Sam_RendellAuthor Commented:
Yup, is reseeding after defrag likely to create long update queues anyway or should the copies all still be up to date?
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endital1097Commented:
the database will still be up-to-date
you are suspending the database copy which will stop log replication
to defrag the database you must dismount it which prevents any new logs

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Sam_RendellAuthor Commented:
Great that is what I wanted to hear. Reading around it seems like 110GB DB could take a looong time to defrag, any guesses?
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endital1097Commented:
if you defrag it to the same disk where the db lives, it will probably take about 4-6 hours
it also depends on the i/o of your disk
i had an 80gb db take 3 hours, but there was a lot of white space

check the application log for 1221 events to see how much
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Sam_RendellAuthor Commented:
I can defrag to separate disks so it should be quicker I guess.
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endital1097Commented:
it's quicker on the same disk
separate disks it must copy the new file to the original location
same disk doesn't copy
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Sam_RendellAuthor Commented:
oh that's bad news I've not got enough room on the same disk.
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endital1097Commented:
yes, think about how long it takes to copy a 110gb file from disk to disk :(
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Sam_RendellAuthor Commented:
Thanks for the help :)
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