## 7.7.1 Methods to identify a disk for use as a virtual SCSI disk 

The VIOS uses the following methods to uniquely identify a disk for use as a virtual SCSI disk: 

GLYPH<SM590000> Unique device identifier (UDID) 

GLYPH<SM590000> IEEE volume identifier 

GLYPH<SM590000> Physical volume identifier (PVID) 

Each of these methods can result in different data formats on the disk. The preferred disk identification method for volumes is the use of UDIDs. 

## 7.8 Windows hosts 

To release new enhancements more quickly, the newer hardware architectures are tested only on the SDDDSM code stream. Therefore, only SDDDSM packages are available. 

For Microsoft Windows 2016, and Microsoft Windows 2012, download the latest version of SDDDSM from this website: 

## 7.8.1 Clustering and reserves 

IBM Support - SDDDSM 

Windows SDDDSM uses the persistent reserve functions to implement Windows clustering. A stand-alone Windows host does not use reserves. 

When SDDDSM is installed, the reserve and release functions are converted into the appropriate persistent reserve and release equivalents to allow load balancing and multipathing from each host. 

## 7.8.2 Tunable parameters 

With Windows operating systems, the queue-depth settings are the responsibility of the host adapters. They are configured through the BIOS setting. Configuring the queue-depth settings varies from vendor to vendor. For more information about configuring your specific cards, see “Hosts running the Microsoft Windows Server operating system” in IBM FlashSystem 9100 Knowledge Center 

IBM FlashSystem 9100 Knowledge Center - Windows Hosts 

Queue depth is also controlled by the Windows application program. The application program controls the number of I/O commands that it allows to be outstanding before waiting for completion. You might have to adjust the queue depth that is based on the overall I/O group queue depth calculation, as described in Chapter 5, “Volumes” on page 101. 

