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 to provide 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 persistence. Configure the SCSI controller as VMware Paravirtual. The example in the following figure 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 5. 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 2 x RAM. For log, configure 0.5-1 x RAM (up to a maximum of 512 GB).
Add the capacity of the data and the log device to get the total required capacity 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 datastore. While the default vSAN storage policy is adequate for the system device, a dedicated storage policy is required for the SAP HANA persistence devices to meet the SAP performance requirements. The following figures show the rules that we defined in the storage policy:
Figure 6. VM storage policy: Availability for the SAP HANA persistence
Figure 7. VM storage policy: Advanced policy rules for the SAP HANA persistence
The vSAN storage policy requirements for the SAP HANA persistence are:
Linux LVM distributes the logical volumes that are used by the application across multiple physical devices—in this case, vSAN devices. Distribute the persistence for the data device across eight physical devices and the persistence for the log device across four physical devices.
In the following example, we needed 500 GB capacity for the SAP HANA data device and 200 GB for the SAP HANA log device—a total of 700 GB for the persistence. Thus, we created eight 62 GB vSAN devices for data and four 52 GB devices for log.
Every volume uses the VM storage policy SAP_HANA and is assigned to the dedicated SCSI controller, as shown in the following figure:
Figure 8. Assigning a VM storage policy SAP_HANA and SCSI controller to each disk
After adding devices to the VM, follow these steps in Linux to partition the devices and add them to LVM:
The best way to do this is to create a text file (for example, fdin.txt) with the following content:
cat fdin.txt | fdisk /dev/sdb
This command creates new LVM partitions on the devices; dev/sdb1 is an example. These partitions can be used as physical devices in LVM.
pvcreate /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1 /dev/sdh1 /dev/sdi1 /dev/sdj1 /dev/sdk1 /dev/sdl1 /dev/sdm1
vgcreate hana-data /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1 /dev/sdh1 /dev/sdi1
vgcreate hana-log /dev/sdj1 /dev/sdk1 /dev/sdl1 /dev/sdm1
lvcreate --name data --size 500G --stripes 8 --stripesize 64 hana-data
lvcreate --name log --size 200G --stripes 4 --stripesize 64 hana-log
mkfs.xfs /dev/mapper/hana—data-data and mkfs.xfs /dev/mapper/hana—log-log
mount /dev/mapper/hana-data /hana/data
mount /dev/mapper/hana-log /hana/log