MsSQL server 2016 on pve Vs ms hyper-v performance problem


New Member
Oct 11, 2021
Good day support staff and community,

I have a problem with mssql server 2016 standard

I migrated a windows 2016 virtual machine with mssql server 2016 from Hyper-v to pve.

The customer reported a sluggish performaces.

I'm using mssql studio to run a test query (which reads a lot of data but writes nothing) and see how long it takes.

In the virtual machine in hyper-v the response of the query the first time takes from 15 to 20 seconds. The next times I run it it always takes 3 seconds. During the tests I ran the query at least 5 times (sometimes even more).

In the pve virtual machine it always takes different times ranging from 15 to 20 seconds. An example: 19,15,16,17,15 etc.

In the hyper-v machine I also tried to move the disks to an external usb drive, to make sure the short response times are not due to disk access.

Although the response times of the virtual machine in normal use are much higher, the first response of the query took more than a minute, but the subsequent responses always 3 seconds.

I tried to migrate the vm in two different hardware with different versions of pve (6.4-4 no updates and 7.0-13) both with zfs.

On pve 6.4-4 I have also tried to create a new machine with windows 2019 and mssqlserver 2016 and doing dump and restore of database.

I tried to create an ubuntu 20 machine with mssqlserver 2019 and doing dump and restore of database

I have performed several tests on the virtual machine hardware (dynamic disk vs fixed, controllers, volblocksize etc). I have always used fixed ram and not balooning.

In all cases in pve I cannot see this optimization for which the same query from the second execution is executed very quickly.

It almost seems as if there is a sort of caching on hyper-v that does not happen on pve.

Thank you for your time and I am looking forward to hearing from you guys.
Hi guys,
we tried to do further tests but without any positive results. I can't understand why there is this difference between pve and Hyper-v with mssql

I hope someone can give me some hint.


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