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Contributor
Contributor

Is VM performance impacted by ESXi being loaded on HDD vs SSD

I am running ESXi v6.5 on 4 hosts. ESXi is installed on the local disks of each host, which are all HDD.

The VMs are all stored on an older SAN and performance is satisfactory, but could be better.

In an attempt to improve performance, 4 TB NVMe SSDs were purchased for each host to be utilized as virtual flash read cache. Unfortunately, there wasn't a noticeable difference in VM performance. 

I am curious, if I upgrade my host hard drives to SSDs and reload ESXi onto those, should I expect any performance enhancements out of my VMs or not?

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Enthusiast
Enthusiast

Hi @cmcdo12000,

Not that I know of. The Virtual Flash Read Cache only benifits the VM's because they use these disks. The ESXi host itself has nothing to do with this as far as I am aware. So upgrading these will not actually do anything.

Please also note that this feature is being deprecated, and is no longer supported in vSphere 7.x.

https://blogs.vmware.com/vsphere/2019/04/vflash-read-cache-deprecation-announced.html 


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No, local disks don't affect VM performance.

Check for the following:

Storage:
- SAN disks: Are they SSD? Are they HDD's? Are they working correctly?
- HBA's: are they working properly? are drivers and firmware up to date?
- What is the iSCSI queue length for the controllers?
- What controllers are you using on your VMS?

Network:
- Which nics are you using (1GBPS/10GBPS/More)?
- Are all nics on the solution the same?
- What nics are you using on your VMs?

- Resources:
How many vCPUs do you have?
How many cores/logical cores does your host have?
Do you have EVC enabled? what level?
How much memory do you have?
What is your overcommitment ratio?

Let me know if you need further assistance. 

 

Please visit my blog at https://nachogonzalez.com.ar
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No, local disks don't affect VM performance. (Unless VMs are running on them)

Check for the following:

Storage:
- SAN disks: Are they SSD? Are they HDD's? Are they working correctly?
- HBA's: are they working properly? are drivers and firmware up to date?
- What is the iSCSI queue length for the controllers?
- What controllers are you using on your VMS?

Network:
- Which nics are you using (1GBPS/10GBPS/More)?
- Are all nics on the solution the same?
- What nics are you using on your VMs?

- Resources:
How many vCPUs do you have?
How many cores/logical cores does your host have?
Do you have EVC enabled? what level?
How much memory do you have?
What is your overcommitment ratio?

Let me know if you need further assistance. 

 

Please visit my blog at https://nachogonzalez.com.ar
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