So I will bite and offer some advice. Been through this a lot (sigh).
First, some of the things to watch for:
1: Naming. Mac users on Mac storage will can use any character they want other than : and /. For example my.file!!@##$>that is so important##$123. . can be a file name. So can *********REALY IMPORTANT FILE!!!!!! Yes there are spaces in the from and end. Yes this will make Window panic. You must do a review of file and folder names BEFORE trying to migrate. Look for files that start and end with the space character. Beware the Windows reserved characters. Clean up your naming before migration. For details, see here https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
2: Maximum path length. Yep. In this day of unicode many parts of Windows can only handle a max file system path of 256 characters. See link above. If you are coming from a system that supported longer paths (like OS X and *nix operating systems) than you will want to review the length of your file paths. Test, test, and test some more with all your tools, including your backup software. Make sure it can both see paths that exceed the API limit and also that it is capable of restoring data in paths that exceed the length.
3: SMB is still a nightmare. From rampant file ID numeration, to slow directory reading, to hung Finder. Your Mac OS version will have varying degrees of success. 10.8 was a mess with DFS. 10.9 was a train wreck with Windows Clustered servers. 10.10 has huge issues with file ID enumeration and periodic deadlock issues. Once again, test in your environment. Get cozy with the nsmb.conf file.
4: Don't let your Macs sleep. AFP supports idle reconnect. Connect to a server, let the mac sleep, on wake it can renegotiate the connection to the server volume (usually). SMB does not do this. If your Macs fall asleep with documents open from the SMB share, you are in a world of hurt.
5: Be prepared to not be able to find anything. Searching on Windows shares has been a frustrating situation. You will not have Spotlight support from the server so you can either use a directory trawling search tool like Find Any File or be prepared to maintain Spotlight indexes on each workstation and hope for the best.
As for the methods to get the data from one place to the other, you need to realize there is a time constraint. Using a 4 GB/min rule of GigE transfer, assuming no issues and no disruptions, the 18 TB of data will take 75 hours to copy. Now, since this is a NAS going to a Windows system, you likely will not get 4 GB/min so increase that number by 20%. If the Windows server has on write virus scanning, add another 10%. If possible the best advice I can give you is to do this in logical chunks. Now, I don't know your data set so this may not be possible. However, if you have multiple shares, move one share per weekend to ensure you have ample time to perform the copy and also to correct any issues that may arise.
Regarding the tools, I've always used rsync because it allows for both detailed logging and also in line incremental runs. Should it get disrupted for any reason, you can pick up where you left off. Sadly, this is not GUI based. Also, the rsync 2.6.3 included with OS X is not adequate in supporting all file system features. I prefer to build a copy of the latest 3 branch. I will also include some of the patches like file flags and hfs-compression. If this is just data, the patches may not be needed. If you need a GUI tool, CronoSync is adequate.
And finally, if you find that SMB on Windows is just too frustrating, there is Acronis Access Connect. This is an add on to Windows server to provide native AFP and Spotlight. In the past few years I have been plagued with SMB issues across numerous versions of OS X. Granted, many of the issues are in corporate environments where I do not have any visibility to the Windows server config. I have no idea what they are doing on those machines, but I do know that OS X integration has been rough.
Hope this helps. Good luck on your project. Test and test some more before putting before your end users.
Reid
Apple Consultants Network
Author - "El Capitan Server – Foundation Services"
Author - "El Capitan Server – Control & Collaboration"
Author - "El Capitan Server – Advanced Services"
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