Best way to approach using EFS is to follow the rules as set forward in the Win2K Resource Kit. Basically, you need to have your recovery agents in place.
This can save you a lot of headaches should the service account get deleted. Recreating an account means it actually gets a different SID. The "name" of the account is for our convenience (and apps like SQL Server). However, as far as the OS is concerned (and therefore EFS), it relies on the SID.
On the local system, the administrator tends to be a recovery agent, so you have an option, usually. Biggest problem, though, is when you have to rebuild a system and you try to get access to the files. Administrator account would be different, etc. You get the idea.
So before implementing EFS, make sure you've got recovery in mind. And make sure you've tested it.
K. Brian Kelley
Author: Start to Finish Guide to SQL Server Performance Monitoring
K. Brian Kelley, CISA, MCSE, Security+, MVP - SQL Server
Regular Columnist (Security), SQLServerCentral.com
Author of Introduction to SQL Server: Basic Skills for Any SQL Server User
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