Just got a question for the mathematically minded ...
I've populated my ReadyNas 4 Ultra with 4 identical disks, Western Digital's RE4 2TB 7200RPM SATA 64MB. All have striped fine.
But in the Volumes tab, I'm told my total disk size is 5234GB, each disk is said to have 1858GB allocated.
How is this figure calculated? I understand it's not going to be 4 x 2TB and that 2 disks together would only give 2TB, but where does 5234GB comes from? I feel as though I've been a bit short changed! 😉
1. Disk manufacturers use 1GB = 1000^3, whereas most modern operating systems, including RAIDiator, use 1GB = 1024^3. This means a 1,000 GB disk will show up as 931 GB in FrontView (and consequently, a 2 TB drive will be 1862 GB) 2. RAID requires one disk capacity to maintain redundancy. This means if you have 4 x 2 TB disks, your end usable capacity will be 3 x 2 TB. 3. RAIDiator operating system takes up roughly 2.25GB per disk. 4. The overhead of RAID and filesystem takes up roughly 2% of the total space. 5. Snapshot space takes up 5GB by default during installation. This is resizable.
In your case, my calculations would yield:
Total capacity = 4 x 1862 GB = 7448 BG Minus 1 disk for redundancy = 7448 - 1862 = 5586 GB Minus 10 GB for OS = 5586 - 10 = 5576 GB Minus 2% = 5576 - 111 = 5465 Minus Snapshots = 5465 - whatever size it's set to
So, I would calculate that you're in the neighbourhood of 5450 GB +/- any discrepancies in snapshot size. Not sure where the extra 200 GB went, though.
Thank you to all for all your detailed responses. Very much appreciated. 😉 I think I have to get my head stuck into this manual a little more and understand snapshots.
