When consulting with an engineering firm planning an Active Directory consolidation, I found the customer was concerned about the time it would take for security translation for their file servers. I explained that even if the file is open the migration software can still translate the ACL, as it only accesses the metadata, not the actual data in the file. This means that an offline maintenance window doesn’t have to be scheduled, but performance might be slow while the translation agent is running on the server.

In addition, the customer was worried because they have 1.5 Terabytes of data, consisting of about 500,000 files, and about 20,000 folders. I explained that the size of data on the server was not as important as the number of objects - files and folders and ACL depth. This company had a large number of CAD drawings, some of which in the hundreds of gigabytes. However, if there are only 5 users and 10 groups on the ACL, security translation will take less than 1 second for this file - no faster or slower than a 39KB Word document. Somehow because it takes a long time to copy a large file, admins think it will take  a long time to translate - but the real deciding factors of performance are the file and folder count, and number of ACE's on the ACL.