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In-place versus side-by-side upgrade

We are planning an upgrade from 7.0 to 8.0 on one of our servers, and we are considering two methods: one a side-by-side install and an in-place upgrade. Hopefully you can help me with a time estimate for the side-by-side install. I have found an estimate for the in-place upgrade. We have a database that is in the 300 GB range, and I am trying to find a time estimate for the DTS detach/attach procedure. I know it will depend on the complexity of the database and objects but was wondering if there is a ball park estimate that I could use? Also I am leaning towards the in-place upgrade and would appreciate any thoughts you have on this method.
Detaching a database is simply closing the database, flushing the transaction log, and removing entries in sysdatabases. Attaching a database is simply placing entries in sysdatabases and opening the database files. It doesn't matter whether the database is 1 MB in size or 1 TB in size. It will depend on the volume of transactions required to be flushed to disk. When you detach a 7.0 database and attach it to SQL Server 2000, it undergoes an additional process of converting the metadata and making necessary changes to system tables, and I have no time estimates on that. Upgrading in place simply means dropping all of the new binaries and updating metadata and system objects. I don't do upgrades via detach/attach. If I'm going to upgrade it, I backup all databases, ensure I have orginal SQL Server 7.0 installation media along with any service packs which were applied in the event I need to roll back to previous version and then just upgrade it in place.

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