Hi Dan,
If you stop the integration service in the windows service manager, does the database continue writing at such high rates?
If there are no scenarios activated, there should be very little SQL traffic.
There could be a problem with the database itself. SQL could be generating indexes.
I've found that if you have less free space on the server hard disk than the size of the largest database on the disk, SQL can run into problems creating indexes.
Regards
Cameron