Drive Storage Capacity Doesn't Add Up

[SandZogg]

I have two 2TB drives in my RN212, but it shows total capacity as 2TB.

It should be 4TB.

Both drives show up on the setup page as functional.

What have I done wrong?

[StephenB · Accepted solution]

It is working as designed (though perhaps not the way you want).

XRAID (the default RAID mode) provides single redundancy, so your data remains available even when a single drive fails.  This takes away from the total volume size.  The general rule for capacity is "sum the drives and subtract the largest" - which works out to 2 TB in your case.

In your specific case, the NAS is using RAID-1, which mirrors the two drives - everything is written to both in parallel.

If you need the extra space, you can either upgrade both drives to 4 TB, or you can back up your data and start over.  You'd do a factory default with only one drive in place, and then switch to flex-raid.  After that you'd insert the second drive and create a second 2 TB volume on it.

[StephenB · Accepted solution]

It is working as designed (though perhaps not the way you want).

XRAID (the default RAID mode) provides single redundancy, so your data remains available even when a single drive fails.  This takes away from the total volume size.  The general rule for capacity is "sum the drives and subtract the largest" - which works out to 2 TB in your case.

In your specific case, the NAS is using RAID-1, which mirrors the two drives - everything is written to both in parallel.

If you need the extra space, you can either upgrade both drives to 4 TB, or you can back up your data and start over.  You'd do a factory default with only one drive in place, and then switch to flex-raid.  After that you'd insert the second drive and create a second 2 TB volume on it.

[SandZogg]

Thanks so much!

I have never used RAID, so now I know how it works.