Why does your '4TB' hard drive show less than half that amount in terms of usable storage? Our Helproom Expert explains.

QUESTION I have an Iomega StorCenter ix2-200. I was led to believe it offered 4TB of storage, yet I can see only 1.79TB. Why is this and how can I find the remaining space? Tim Burchell

HELPROOM ANSWER The Iomega StorCenter ix2-200 is available in 1TB, 2TB and 4TB versions. The first step is to ensure that you have been sent the 4TB version of the drive.

According to the manual, the drive comes with its twin hard drives configured in a Raid 1 array. This means the second hard drive functions as a mirrored copy of the first – it doesn't contribute any capacity to the total amount of storage.

A Raid 1 setup prevents a failure of either hard drive resulting in data loss – the information is backed up on to the second drive. You can replace the faulty drive and the unit will automatically restore the backup, while maintaining access to your files.

This means the total capacity available to you will be that of just one of the two 2TB hard drives. The usable formatted capacity of each drive is somewhat lower than the specified 2TB, however, which is why you see just 1.79TB.

If you need storage space more than you need the protection of a Raid 1 setup, switch the array mode to Jbod. This will combine both 2TB drives into a single 4TB volume. However, when either of these drives fails, all data stored on that drive will be lost.

The StorCenter can't convert between these two array modes while preserving your data, so if you want to convert from Raid 1 to Jbod you'll first have to back up all the data on the drive elsewhere.

Next go to the Settings tab and select Disks, Manage Disks. From here you can specify your desired data-protection option and re-build the drive array.

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