Estimating required FMD capacity

Hitachi Data Reduction Estimation Tool can estimate data reduction efficiency achieved through all of the following data reduction capabilities provided by Hitachi Virtual Storage Platform (VSP) G and F series:

• Deduplication and compression Achieve storage efficiency savings by deduplication and compression through storage controller.
• Accelerated compression With Hitachi Accelerated Flash DC2 (HAF DC2), Hitachi Accelerated Flash DC2 (HAF DC2), VSP G and F series offer even greater benefits through scalable hardware-accelerated compression. You can answer business demands for high performance and deliver the lowest effective cost.

You can estimate the data reduction rate by following the GUI wizard. The window displays the calculation results in a graph. You can use the graph to compare and check the results.

Parent Topic

• Estimating required FMD capacity

When you need to install FMD drives to create a new pool, use the following workflow to estimate the required capacity.

1. Estimate the required pool capacity.

   Estimate the pool capacity required for user data in the same way you estimate capacity when creating a pool.

2. Estimate the Saving % using one of the following methods:
   • If data will be migrated to the FMD, use the Data Reduction Estimation Tool to estimate the Saving %. The tool reports a Saving % that can be used to determine the capacity needed. If the estimate is less than 20%, best practice is to use a parity group with accelerated compression disabled, and to estimate the pool capacity by the conventional method.

   • If new data will be stored on the FMD, or if the Data Reduction Estimation Tool cannot be executed in the environment, consider setting the Saving % to 0% and using the conventional method to size capacity. With accelerated compression disabled for the parity group, you can monitor the Saving % through the management software and then decide to enable accelerated compression at a later time.

   NoteIf the 14-TB FMD is used and the Saving % that is estimated in this step exceeds 75%, apply 75% for "Saving %" in the formula of the next step.

3. Estimate the required FMD capacity to be purchased.

   If there is data to migrate to the FMD, use the following formula to calculate the required FMD capacity.

    Required FMD capacity to be purchased = 
   			 required-pool-capacity * (100% - (Saving % - 10%)) * 110% 
   		  

   The buffers in the above formula are as follows:

   • - 10%: Buffer representing expected increase in capacity because of degradation in Saving %
   • * 110%: Buffer representing expected increase in capacity because of additional space required to store management information of the storage system

   Then, enable accelerated compression and create parity groups, LDEVs, and pools.

   Note

   When using Dynamic Tiering or active flash, if the Tier 1 is configured of FMD drives, use 1.2 times the calculated required pool capacity. Use the following formula to calculate the value:

    Required pool capacity = 
   				required-pool-capacity-estimated-in-Step-1 * 120% 
   			 

   To prevent the depletion of assured capacity for writing due to the tier relocation, Dynamic Tiering or active flash uses a 20% buffer when calculating the number of pages that can fit in the FMD tier. If accelerated compression is disabled, Dynamic Tiering or active flash do not use the 20% buffer.

   Therefore, if the same FMD (Tier 1) capacity is applied, the amount of data that can be stored with accelerated compression enabled is smaller than the amount of data that can be stored with accelerated compression disabled.

Parent Topic

• Estimating required FMD capacity

When you need to install additional FMD drives to expand an existing pool, use the following workflow to estimate the required capacity.

1. Estimate the pool capacity to be added.

   Estimate the pool capacity required for user data in the same way you estimated capacity when creating a pool. If you are expanding a pool, also estimate the additional capacity.

2. Check the Saving %.

   The Saving % is displayed in the Pools window. View the Saving % by clicking Pools FMD Pool Volumes Capacity Saving (%).

   NoteIf the 14-TB FMD is used and the Saving % confirmed in this step exceeds 75%, apply 75% for "Saving %" in the formula of the next step.

3. Estimate the required FMD capacity.

   Use the following formula to calculate the required FMD capacity:

   Required FMD capacity = Required pool capacity × [100% - (Saving % - 10%)] 
   		  

   The buffer in the above formula is as follows:

   • - 10%: Buffer representing expected increase in capacity because of degradation in Saving %

   Estimate the additional FMD capacity to be purchased according to the required FMD capacity calculated using the above formula, and the free capacity assured for writing.

4. Check the free capacity assured for writing.

   In the Pools tab of the Pools window, check the value of FMD Pool Volumes Capacity. The free capacity reserved for writing is the difference between the Total and Used values.

5. Estimate the additional FMD capacity to be purchased.

   If the space calculated in step 4 is sufficient, this step is unnecessary. If the space is insufficient, use the following formula to calculate the required FMD capacity:

   Required FMD capacity to be purchased = (Required FMD capacity - free capacity assured for writing in step 4) × 110% 
   		  

Parent Topic

• Estimating required FMD capacity