Dell EqualLogic PS6210XS EqualLogic Group Manager Administrator s Guide PS Ser - Page 158

The volume reserve is equal to the reported size. For example, even if only 10 percent of a volume is in use, the group allocates the full reported size. • Thin provisioning enabled The volume reserve is equal to or less than the reported size, depending on volume usage and the thin-provisioning settings. Initially, the group allocates the minimum amount of volume reserve for a thin-provisioned volume. The minimum is 10 percent of the reported volume size or the user-specified percentage. As initiators write to the volume, free volume reserve decreases. When free volume reserve falls below a threshold, the group increases volume reserve, up to a user-defined maximum (assuming available free pool space): • For a volume with a reported size of 100GB or greater, when free volume reserve is less than 6GB, the group allocates an additional 10GB. • For a volume with a reported size that is less than 100GB, when free volume reserve falls below 6 percent of the reported volume size, the group allocates an additional 10 percent of the reported volume size. Event messages inform you when in-use volume reserve surpasses a user-defined limit and reaches the maximum. Enable Thin Provisioning on a Volume When you create a new volume or clone an existing volume, you can enable thin provisioning on the volume. In addition, you can modify an existing volume and enable thin provisioning. You can make these changes while the system is running. Thin provisioning is not appropriate for all environments or volumes. You must fully understand thin provisioning before implementing the functionality on a volume. When enabling thin provisioning on an existing volume, the following considerations apply: • Enabling thin provisioning on a volume usually decreases the amount of space that the group allocates to the volume (called the volume reserve). • Enabling thin provisioning changes the amount of allocated snapshot space and replication space, because the group allocates snapshot space and replication space based on a percentage of the volume reserve. However, the group increases the snapshot space and replication space percentages to prevent the deletion of snapshot or replication data. To enable thin provisioning on an existing volume: 1. Click Volumes. 2. Expand Volumes and then select the volume name. 3. Click Modify settings. 4. Click the Space tab to open the Modify Volume Settings - Space dialog box. 5. Select Thin provisioned volume. The Pool Space table values change. 6. (Optional) Modify the groupwide default thin-provisioning space settings: • Minimum volume reserve • In-use space warning limit • Maximum in-use space (maximum volume reserve) 7. Click OK. Make sure that you carefully monitor the space usage for a thin-provisioned volume. 158 About Volumes