How to sync three or more external Hard Drives

I guess if you need a once a month backup of data to a NAS, it would be easiest if each tech ran a small software/script that would sync anything that's not older than 30 days.

I would recommend Robocopy in that case. You can create a script that would copy from an external drive to a network share or mapped network drive and then specifiy a MAXAGE of the files to copy. If you set that to 30, then nothing older than 30 days will be copied.

Robocopy is part of Windows now or can be obtained freely from Microsoft.

If you wanted to copy any files from the D: drive to the "Support" share on "NAS", excluding directories A1, B2, C3, showing you the output and copy nothing that is older than 30 days, it would look something like this:

robocopy "D:" "\\nas\support" /E /ETA /TEE /XD "D:\A1" "D:\B2" "D:\C3" /MAXAGE:30 /R:5 /W:5 /LOG:copy.txt

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That would copy anything up to 30 days old (file/folder creation) from D: to \\NAS\SHARE with detailed output, ignore 3 directories on D: and create a logfile in the folder you run this command from.

R: and W: are the number of retries of copying fails and how long to wait between retries.

Not sure if this is what you're looking for, but it would be one script and could be run from a Desktop shortcut.

I am looking for at least a 2 way sync between each person's external and the NAS. What I am really looking for is a way to sync all files to all 10 external hard drives simultaneously. I not too worried about the age as much as making sure at least the newest of each customer's files are on all external hard drives.

I'm using SyncToy from Microsoft for similar purposes.  
And Second Copy is appropriate for a bit more ambitious schemes.