Special requirements apply to configuring the persistence (data and log) of an SAP HANA VM.
Dell EMC recommends using Linux Logical Volume Manager (LVM) devices for the SAP HANA persistence. LVM enables a striping of the logical volumes across multiple vSAN devices, which provides better performance and flexible administration. LVM also enables resizing of logical volumes if capacity adjustments are required.
The following sections provide step-by-step instructions for configuring the SAP HANA persistence on Linux LVM devices.
A VMware best practice is to use a dedicated SCSI controller for the SAP HANA data and log devices. Configure the SCSI controller as VMware Paravirtual. The following example uses SCSI Controller 0 for the system device, SCSI Controller 1 for the LVM data devices, and SCSI Controller 2 for the LVM log devices:
Figure 3. VM SCSI controller for the SAP HANA persistence
Use the SAP Quick Sizer tool to determine the required capacity for the SAP HANA data and log devices. If the sizing details are not available, Dell EMC recommends configuring the sizes of the data and log devices based on the memory size of the SAP HANA VM. For data, configure 2x RAM. For log, configure 0.5-1x RAM (512 GB maximum for log).
Add the capacity of the data and the log device to get the total capacity required for the SAP HANA persistence of the VM.
You must define a storage policy for the SAP HANA LVM physical devices that are deployed on the vSAN data store. While the default vSAN storage policy is adequate for the system device, the SAP HANA persistence devices must have a dedicated storage policy to meet the SAP performance requirements. The following figure shows the rules that we defined in the storage policy for the SAP HANA persistence:
Figure 4. VM storage policy for the SAP HANA persistence
The vSAN storage policy requirements are:
The optimal number depends on the number of available disk groups and capacity disks. The minimum (default) is 1 and the maximum is 12.
Linux LVM distributes the logical volumes that the application uses across multiple physical devices—in our case, vSAN devices. We recommend distributing the persistence for the data device across eight physical devices and distributing the persistence for the log device across four physical devices.
In the following example, we need 500 GB capacity for the SAP HANA data device and 200 GB for the SAP HANA log device, yielding a total of 700 GB for the SAP HANA persistence. We therefore create eight 62 GB GB vSAN devices for data and four 52 GB devices for log.
Every volume uses the VM storage policy “HANA PERSISTENCE” and is assigned to the dedicated SCSI controller, as shown in the following figure:
Figure 5. Assigning a VM storage policy to the devices
After the devices have been added to the VM, perform the following steps in Linux to partition the devices and add them to LVM:
This command creates new LVM partitions on the devices, for example, /dev/sdb1. These partitions can be used as physical devices in LVM.
Repeat this command for every device that you create for the SAP HANA persistence.
lvcreate --name log --size 200G --stripes 4 --stripesize 64 hana-log
Use the number of physical devices that you created earlier as the --stripes parameter