Yes you can add the drives to your NX3230 and add the space while the system is in production. What I would recommend is that you first get a backup of all your data on the system before you expand the virtual disk. Also what I would do is to do the expansion when the system is at a low I/O time. When you do the expansion it will slow the virtual disk some while the expansion is in progress.
Please let us know if you have any other questions.
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