Is it necessary for the guest OS to support SSD if the virtual machine file is placed on a SSD?

[WaleyWang]

Dears,

I have a plan to set up a virtual machine file on a SSD disk. The host system is windows 10 (on another SSD, I'll use 2 SSD), it should support SSD very well.  Then comes the question: should I also install a guest OS which need also support SSD?

My opinion is that it does not matter since the disk I/O operation is done by host OS, it is the host OS who finally determin whick block the data will be writed to (disk optimization).

Am I correct? Thanks.

[linotelera]

Hi and welcome...

yes is correct when guest OS is driving a vmdk file in a ssd disk. I suggest the SSD specific OS driver in case of raw device utilization.

Regards

[WaleyWang]

Hi, linoteleralinotelera,

Thanks for the answer! While I did not really understand your mean. Do you mean that it is nessary for the guest OS to support SSD or not? For example, if the guest OS is windows server 2003 (it has no optimization tool for SSD disk), will it potentially be harmful for the SSD disk? Thanks.

[linotelera · Accepted solution]

Sorry for cryptic answer...

In your case the answer is yes: it doesn't care about the type of the media, while virtual disk is a vmdk (handled as virtual hardware) and placed in a SSD.

There are some rare cases where you could use physical disk directly to virtual machine (known as raw disk device or RDM in vSphere environment).

Regards

[_Royce_]

The disk inside the guest will be some kind of VMware virtual device depending on what options were set when the VMDK was created.

eg. "VMware virtual SATA Hard Drive" is the disk inside my guest win 10 running on my mac.

The answer to the question is NO - it is not necessary for the guest to support SSD. The guest doesn't need the same drivers as the host for the physical storage device because the guest doesn't see the physical storage device, it only sees a virtual one.

[NoelC1]

One additional point (and if this is obvious I apologize):

If you want to reduce the write load on your SSD - which with SSDs built after about 2012 isn't really a strong worry as the controllers are quite smart about wear leveling - you could consider deconfiguring the automatic defragmentation in the guest (e.g., shutting it off).

-Noel

[_Royce_]

On my win 10 guest, under Optimize Drives settings it automatically has status "Optimization not available". Perhaps other guest OS's may not do that.

[NoelC1]

status "Optimization not available"

From what I recall, that implies WinSAT on the guest has determined the performance of the disk to be high enough that it's an SSD, and that the VMware virtual disk refuses to respond to a TRIM command.

This thread is about guests old enough that they don't have that WinSAT determination.

-Noel