Capacity design principles (1) : Physical capacity (for HPEC 4D+2P)

The physical capacity in drives is classified into the following two categories:

• Valid physical capacity [MiB] (totalRawCapacity): The amount of space that has been available since the drive was added to the storage pool.

• Physical capacity of control information [MiB] (metaDataPhysicalCapacity): The capacity for control information in the total capacity (total physical capacity) of the drives allocated to the storage pool.

For HPEC 4D+2P, the effective physical capacity (C_rawDevice [MiB]) is determined by the following calculations:

The following formula is an approximate expression and there might be a margin of error of up to 1 GiB.

CrawDevice = floor((Cdevice × 512/(512+8)) - 2048[MiB] - 148932[MiB], 148932[MiB])
    floor(value, reference value)
        : The value is rounded off to a multiple close to the reference
          value.
    Cdevice: Drive capacity[MiB]