Calculate the storage avaliable capacity

Available Capacity Calculation Method

The following uses an example to explain how to calculate the allowed expansion capacity. Three valid digits are retained after the decimal point.

Assume that forty-eight 600 GB SAS disks will be added to the storage system, including four coffer disks and the hot spare policy and RAID policy are configured to Low and RAID 6 (8D + 2P) respectively. The allowed expansion capacity is calculated as follows:

1. 600 GB is the nominal capacity provided by the disk vendor. Use the following method to convert this capacity to one that can be identified by the storage system:

   600 GB x (1000/1024) x (1000/1024) x (1000/1024) = 572204.590 MB

   OceanStor 5300 V3/5500 V3/5600 V3/5800 V3/6800 V3 storage systems provide the DIF function for end-to-end data protection. This function takes 1% to 2% of storage space. The following uses 2% as an example.

   572204.590 MB x (1 – 2%) = 560760.500 MB

2. Minus the WriteHole capacity:

   560760.500 MB – 256 MB = 560504.500 MB

3. Minus the reserved production space:

   560504.500 MB – 577 MB = 559927.500 MB

4. Minus the metadata capacity:

   559927.500 MB x (1 – 0.6%) = 556567.935 MB

   NOTE: The storage system reserves 0.6% of each disk's space as metadata space. It dynamically allocates metadata space as services increase. The actual services prevail. The following uses 0.6% as an example.

5. Minus the metadata backup capacity:

   556567.935 MB x (1 – 2%) = 545436.576 MB

6. Minus the reserved space for improving system performance and disk balance:

   545436.576 MB x (1 – 1%) = 539982.210 MB

7. Minus the integrated capacity: 539982.210 MB x 98.46% = 531666.484 MB

8. Because the hot spare policy of the storage system is set to Low, capacity of two disks is used as hot spare space capacity. Therefore, the remaining capacity is as follows after the hot space capacity is deducted:

   531666.484 MB x (48 – 2) = 24456658.264 MB

   Equals to 24456658.264 MB/1024/1024 = 23.324 TB

9. Minus the coffer data capacity:

   23.324 TB – 4 x 5 GB = 23.304 TB

10. Because the RAID policy of the storage system is RAID 6 (8D + 2P), the disk utilization is 80%. Therefore, the allowed expansion capacity is:

    23.304 TB x 80% = 18.643 TB

In this example, the allowed expansion capacity is 18.643 TB.

NOTE: The preceding available capacity is for reference only. The capacity displayed on the DeviceManager management page prevails.