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A virtual machine cannot run properly without virtual disks, which is to say, it must have at least one virtual storage controller that works to connect the disk. For Hyper-V VM users, IDE and SCSI are 2 virtual storage controllers that they can choose from when creating a virtual machine. Which one is better? How do they differ from performance, storage capacity, and other factors we care about most? This blog is going to give you some suggestions based on this issue.
IDE Controller
IDE controllers service as emulated devices inside the virtual machine, which means extra processing before I/O will be sent to the disk. For a single Hyper-V VM, you can add up to 2 IDE controllers, and each controller can connect 2 disks. You can boot from IDE drive, and IDE device must be the one that startup disk is attached to. For the startup disk, it can either be a physical disk, or a virtual hard disk.
In generation 1 Hyper-V VM, the guest OS of the virtual machine can only be booted with the help of IDE device, but more options are given to you when choosing the physical device that offers IDE device the storage resources.
SCSI Controller
SCSI controller is a synthetic device which is not emulated like IDE controller. It uses a specifically designed device to work with Hyper-V VMs, and communicates through VMBUS (Virtual Machine BUS. VMBUS works after the boot of guest OS, so SCSI cannot be the startup disk of a virtual machine. Since SCSI controllers utilize existing Windows driver architecture, they are used more for non-operating system disks than IDE disks.
Compared with IDE controllers, SCSI has a huge improvement in terms of storage capacity. For a single Hyper-V VM, you can add up to 4 SCSI controllers, and each controller can connect 64 disks, which makes it a total of 256 disks.
IDE vs. SCSI: How to Choose?
IDE | SCSI | |
Expansion | Low. IDE allows 2 devices per channel. A Hyper-V VM can add up to 4 IDE devices. | High. SCSI allows 64 devices per channel. A Hyper-V VM can add up to 256 SCSI devices. |
Deployment Complexity | Easy to set up. | More difficult than IDE. |
Performance | No huge performance gap in most actual production scenarios. But 10000+ RPM drives are often only available for SCSI. | |
Extra Resources | No additional resources required, unless it’s needed to add extra drives for special occasions. | SCSI needs interface expansion card to function properly. |
Overall Cost | Cheaper | More expensive |
In conclusion, the overall performance between IDE and SCSI has no very huge difference, and the former one can be more cost-effective. But if you want to make best of a Hyper-V VM by utilizing both controllers, one of the best practices is to create a Generation 1 VM with guest operating system installed on IDE Controller 0, Location 0, paging file in a virtual hard disk on IDE Controller 0, Location 1, and one or more disks on SCSI controllers.
In order to prevent data stored in the virtual disks, no matter they’re IDE or SCSI based, from being lost in disaster or ransomware attacks, having an effective and advanced Hyper-V backup plan is important. Vinchin Backup & Recovery is a cutting-edge enterprise backup solution that offers a series of backup and restore features for 10+ virtual platforms including Hyper-V, which helps you backup Hyper-V VMs at ease through a single web-based console. The software offers a 60-day full-featured free trial, download it now to get the journey started.
Wrap up
The blog introduces the major differences between IDE and SCSI, the 2 virtual storage controllers in Hyper-V VMs. When allocating the disk resources in Hyper-V VM creation process, you should take the actual production environment including OS requirements, commonly used applications, etc., into consideration, to drive the best performance.
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