This section presents a method to expand a VMFS by utilizing the non-disruptive expansion capability of the PowerMax.
vSphere offers VMFS Volume Grow, which allows one to increase the size of a datastore that resides on a VMFS volume without resorting to physical extent spanning. It complements the dynamic LUN expansion capability that exists in PowerMax storage arrays. If a LUN is increased in size, then VMFS Volume Grow enables the VMFS volume to dynamically increase in size as well. Often, virtual machines threaten to outgrow their current VMFS datastores and they either need to be moved to a new, larger datastore or the current datastore needs to be increased in size to satisfy the growing storage requirement. Prior to this capability, the option for increasing the size of an existing VMFS volume was to extend through a process called spanning. Even if the newly available space was situated upon the LUN which the original VMFS volume resided, the only option was to add an extent. A separate disk partition was created on the additional space and then the new partition could be added to the VMFS volume as an extent. With VMFS Volume Grow the existing partition table is changed and extended to include the additional capacity of the underlying LUN partition. The process of increasing the size of VMFS volumes is integrated into the vSphere Client.
It is important to note there are four options when growing a Virtual Machine File System in vSphere. The following options are available when expanding VMware file systems:
- Use free space to add new extent—This options adds the free space on a disk as a new datastore.
- Use free space to expand existing extent—This option grows an existing extent to a required capacity.
- Use free space—This option deploys an extent in the remaining free space of a disk. This option is available only when adding an extent.
- Use all available partitions—This option dedicates the entire disk to a single datastore extent. This option is available only when adding an extent and when the disk you are formatting is not blank. The disk is reformatted, and the datastores and any data that it contains are erased.
The recommended selection is the “Use free space to expand existing extent” option as using this choice eliminates the need for additional extents and therefore reduces management complexity of affected VMFS.
The process to grow a VMFS by extending a PowerMax volume is listed below:
- In vCenter Server, as seen in Figure 31, the datastore EXPAND_DS is nearly full. The underlying device has no additional physical storage for VMFS expansion. The datastore consumes ~30 GB available on the device. Using VMFS Volume Grow and non-disruptive expansion, this issue can be resolved.
Figure 31. VMFS datastore before being grown using VMFS Volume Grow
- The first step in the expansion process is the identification of the device that hosts the VMFS. As shown in Figure 32, Dell VSI can be used to obtain the Volume ID of 000E8.
Figure 32. Identifying the PowerMax volume to be expanded
- Now expand the identified device using Unisphere for PowerMax or in Solutions Enabler as seen in Figure 33.
Figure 33 Expanding a device in Solutions Enabler
- Once complete, a rescan needs to be performed on the ESXi host server to see the expanded volumes larger size. For this example, the device was expanded from 100 to 200 GB. Once a rescan has been executed, the VMFS datastore can be grown. To do this in vCenter, navigate to the datastores listing on any ESXi host that uses the specified VMFS datastore.
- Select the datastore and right-click to expose the menu. Select Increase Datastore Capacity which is shown in Figure 34.
Figure 34. Increasing datastore capacity in the vSphere Client
- The wizard now appears to expand the datastore. In the first step select the device expanded in step 3. The correct device will be apparent by looking at the Expandable column and seeing a “Yes”. In step 2 VMware will automatically select the available space, in this case 100 GB. Step 3 shows a summary. These steps are seen in Figure 35.
Figure 35. Expand datastore wizard
- Finally, view the new size of the expanded datastore in Figure 36.
Figure 36. Completed datastore expansion
SRDF device expansion
The PowerMax supports dynamic, online expansion of all SRDF pairs except SRDF/Metro until PowerMaxOS release 5978.444.444 when online SRDF/Metro expansion is offered. The following section will present the steps to dynamically expand an SRDF device.