Exchange upgrade & Single Instance Storage

[Bob Harris]

I'm about to upgrade from E5.5 to E2k and at the same time replace the server.
After reading many whitepapers the suggested method was to build the new server in the same site then move the mailboxes. I built a test domain and the testing was going well until I read a footnote which mentioned the fact that single instance storage would be lost. The author of the article didn't think this was an issue but with an 8GB private information store and a single instance storage ratio of 4 it seems that there is no way to do a mailbox move without breaking the 1GB limit. I'm surprised that this problem isn't the first item in any checklist but none of the articles I've read even mention it.
As far as I can tell , my only choice is as follows:
Back up the 5.5 server then take it off line
Set up the new server with the same name as the old one
Install 5.5 on the new server using the same site name, ou etc.
Restore the backup to the new server
Upgrade the new server to E2K

Would anyone like to ocment on this?

Bob Harris
Network Administrator
Tauranga District Council
New Zealand

[Colin Janssen]

Hi Bob,

This is an interesting topic, and there are many articles around that actually confuse things. However whilst it is true in a sense that it will be broken, it will be basically recreate on the new server.

All messages have a Message ID. This Message ID is what helps Exchange keep track of single instance storage. There is no sharing of single instance between servers (or storage groups for that matter), however what happens is, as you move the messages across to the new server, the single instance get's rebuilt because the message ID still remains intact.

Hope this answers your question. I have a heap more info on this, as well as some MS articles that state the same. Let me know if you need any more help.

Regards

Colin Janssen


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Bob Harris at 11/13/2002 4:48:25 AM


I'm about to upgrade from E5.5 to E2k and at the same time replace the server.
After reading many whitepapers the suggested method was to build the new server in the same site then move the mailboxes. I built a test domain and the testing was going well until I read a footnote which mentioned the fact that single instance storage would be lost. The author of the article didn't think this was an issue but with an 8GB private information store and a single instance storage ratio of 4 it seems that there is no way to do a mailbox move without breaking the 1GB limit. I'm surprised that this problem isn't the first item in any checklist but none of the articles I've read even mention it.
As far as I can tell , my only choice is as follows:
Back up the 5.5 server then take it off line
Set up the new server with the same name as the old one
Install 5.5 on the new server using the same site name, ou etc.
Restore the backup to the new server
Upgrade the new server to E2K

Would anyone like to ocment on this?

Bob Harris
Network Administrator
Tauranga District Council
New Zealand

[Jim Smart]

Hi Jason,
I had used exmerge to remove many oversized emails sent out to a user list, unfortunately I was unaware of the single instance loss <grin>. My db has now ballooned to 27 GB from 18 GB. I can still handle the size but it now complains about being past the 25 GB limit which I think is an easy reg hack. My question is how can, or can I , get my store back down to the 18 GB limit IE recreate the single instance? One tech article mentioned exporting (exmerge) each mailbox to a .pst, recreate the priv.edb then import back into the new store. But does this restablish the single instance. Secondly does single instance work on any new messages sent to mailboxes or is it broken for good after using exemerge?
Thanks for your help
JT