The minimum number of drives in an SC180 expansion enclosure is 28 (one full, front row in the top drawer and one full, front row in the bottom drawer). Also you need to remember that you will need one spare disk for each disk type. So using the example that have you will have 28 drives & have 26 license. You don’t need any license for your spare drives as they will use the same license of the failed drive.
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