I have HP server with 8 hard drives of 300 Gb attached to RAID controller. When I created one logical disk on every physical disk of maximum size, size of every logical disk is 279,4 Gb. Why logical disk is smaller to 20 Gb that physical one? Is any way to determine size of future logical disk for existing physical disk? For example, if physical disk is 400Gb, what maximum size of logical disk will be?
The capacity that is advertised (e.g. 300GB) is a decimal number. What you see on the raid is a binary number - it differs in such that 1000 bytes in decimal equals 1024 bytes in binary. So your binary GB's are only about 95% of your decimal GB's (e.g. 300GB/1024/1024/1024)
This is mostly due to marketing and normal.