SCSI Ramdisk & Direct IO Ramdisk

The VSuite Ramdisk provides two types of ramdisk using different simulation technologies: SCSI Ramdisk and Direct IO Ramdisk. This section makes a comparison between them.

The SCSI Ramdisk is subject to the SCSI specification and more like a physical hard disk. It can be recognized by the Windows Disk Management and almost all other third-party disk management utilities.

The Direct IO Ramdisk is designed for faster access speed. It uses direct I/O method to access data and consequently reduces a lot of internal system transfer and process time which in turn shows better performance than the SCSI Ramdisk. The cost of peformance improvement is that the Direct IO Ramdisk is treated as a logical disk by the Windows OS and may not be seen by some third-party disk management utilities. And Direct IO Ramdisk can't support ReadyBoost feature, as well as VHD feature. (IMPORTANT: Please don't create or attach the VHD files on Direct IO Ramdisks via Computer/Server Management, otherwise BSOD occurs. It is no problem on SCSI Ramdisks.)

The following figure shows two ramdisks created by the VSuite Ramdisk. Drive R is a SCSI Ramdisk while drive T is a Direct IO Ramdisk. They are both displayed in the Windows My Computer.

However only drive R is found in the Windows Disk Management.

Although drive T is not recognized as a physical disk, it has better access performance. You may find the performance comparison from here.