Expanding the Capacity of a Disk Pool

Precautions

After the capacity of a storage pool is expanded, when the storage pool is in the Migrating data status and the system service load is less than 40% of the upper limit:

• The performance will decrease by no more than 30% if the number of added nodes does not exceed twice the number of existing nodes in the storage pool.

• The performance will decrease by no more than 50% if the number of added nodes exceeds twice the number of existing nodes in the storage pool.

Procedure

1. Choose Resources > Resources > Storage Pool.
2. Click the name of a desired storage pool. On the page that is displayed, click the Disk Pool tab.
3. Click More on the right of a desired disk pool and select Expand Capacity.

   The Expand Capacity page is displayed.

4. Select the Node or Disk tab.
   • Node
     1. In the list, select desired nodes and disks to be added to the disk pool.
        

        • You can click Add and select nodes and disks in the cluster to add them to the disk pool on the Choose Node and Disk page that is displayed.
        • You can select one or more added nodes or disks and click Remove to remove them.
        • After the disk pool is expanded, the system automatically creates VBSs for new nodes in the disk pool. You can choose Monitor > Task Center to view the creation progress.
     2. Select whether to increase the number of data fragments in the disk pool during capacity expansion.
        1. Select Increase Data Fragments During Expansion.
        2. Click Scan to obtain the number of data fragments that can be used for expansion.
           

           If the nodes or disks selected for capacity expansion change, click Scan again to obtain the number of data fragments that can be used for expansion.

        3. Select a value for the Data Fragments After Expansion parameter.
           

           • For details about the usage of different redundancy ratios and the relationship between the number of nodes and the number of available data fragments, see the EC redundancy ratios table in Functions and Features > Key Features > Block Service > EC and Multi-Copy > Elastic EC in the Product Description.
           • You cannot reduce the data fragments once you increase them during capacity expansion for a disk pool.
           • After you increase the data fragments in a disk pool, the total available capacity of the disk pool may not reach the expected value immediately. The specific rules are as follows:

             1. If the used capacity of the disk pool accounts for less than 30% of its total available capacity before data fragment increase, the total available capacity of the disk pool can reach the expected value immediately after data fragment increase.

             2. If the used capacity of the disk pool accounts for 30% to 80% of its total available capacity before data fragment increase, the total available capacity of the disk pool will not reach the expected value immediately after data fragment increase. Instead, it will gradually increase to the expected value as background tasks are running.

             3. If the used capacity of the disk pool accounts for more than 80% of its total available capacity before data fragment increase, the total available capacity of the disk pool will remain unchanged after data fragment increase and gradually increase to the expected value as background tasks are running.

   • Disk
     1. Click the Disk tab.
     2. Select one or more desired disks on the nodes that have been added to the disk pool and add them to the disk pool.

5. Click OK.
6. Confirm your operation as prompted.