In the VMware environment, the MDM, and SDS components are installed on a dedicated SVM, whereas the SDC is installed directly on the ESX host. The PowerFlex volumes that are defined over the Storage Pools can be formatted as VMFS datastores, and then exposed using the ESXi host to the virtual machine or can be used as RDM devices. Once an SDC is mapped to a volume, it immediately gets access to the volume and exposes it locally to the applications as a standard block device. Device management is performed using the SVM, yielding the best I/O performance.

VM storage controller and virtual drives

In a virtual environment, having multiple virtual drives to maximize the parallel I/O streams for best performance and lowest latency as there is a limit of 32 IO queues per LUN or volume in most of the Linux OSs. Dell EMC recommends having at least four to six database virtual drives and adds more disks, depending on the capacity requirements, to achieve better performance.

It is best practice to create multiple virtual SCSI controllers to split operating system and database files as support I/O requirements. The guest operating system virtual drive should be on the primary controller. More controllers are created to separate the virtual drives for datafile, logfiles, and archive logs.

The following table shows an example configuration of controllers and virtual drives for an Oracle database VM:

Table 2.              Virtual adapter and virtual drive details

Use the default adapter type LSI Logic SAS for SCSI controller 0.

Choose Paravirtual SCSI (PVSCSI) adapter type for controllers where virtual drives are used for datafile, redo logs, and archived logs. The PVSCSI adapters are high-performance storage adapters that can provide greater throughput and lower CPU utilization. They are best suited for environments where hardware or applications drive a high amount of I/O throughput.

Shared virtual drives using multiwriter option

In an Oracle RAC database, multiple database VMs must access the same set of virtual drives for read/write operation. By default, sharing a virtual drive was disabled by VMware vSphere to prevent a VM inadvertently accessing another VM’s data. VMware’s VMFS multiwriter addresses this, providing for simultaneous read/write operations across VMs.

The following figure shows an example of how the multiwriter flag for a shared VMDK is set using the vSphere Web Client for VMDKs backed by VMware hyperconverged infrastructure.

Figure 7.              Shared VMDK using multiwriter option

Enabling virtual drive UUID

It is necessary that virtual drives always present a consistent UUID to the guest VM, thus enabling virtual drives to be mounted properly. In VMware vSphere, you must set the disk.EnableUUID parameter for each VM to TRUE.