Slow Server 2019 Disk Performance

Copper Contributor

I recently built a cluster of new to me Dell R620s, which run HyperV with various services.  I noticed right away that these servers were running slower than our old servers, with poor mysql performance and folder transfers.  I then spent the next three weeks tweaking every windows and bios settings I could find, updating everything, and purchasing different Nics, raid controllers, and drives in an attempt to fix it.  The problem was mainly with small io intensive tasks.  A folder with thousands of small files would copy over on local disks in 23 seconds on my old server, but take 2 min 40 sec on the new servers.  Large file transfers were fine however.  The fastest way to test and compare the problem was to use crystaldiskmark, and look at the 4k random tests, since sequential tests performed fine.  The Q1T1 for example would run 21mb read / 24mb write on the new server, and 35 / 38 on the old server.  Finally it occurred to me to fire up an old 2008r2 VM on my 2019 hyper-v host, and to my surprise the number were a good bit better at 25 / 30.  So with that, I scrapped 2019 completely for 2016 on the host, and sure enough it ran 74 / 65 right out of the gate.


Now if someone has any ideas of what's wrong or changed in 2019, I'd love to save having to rebuild the entire cluster.  Of course the strange thing is that a 2019 VM ran even slower than a 2008r2/2016 VM on a 2019 host, which I would think would eliminate most of the driver issues on the VM level.  Hopefully this helps someone out there, and at the very least points out that there are still serious issues with 2019.

9 Replies

@d3mon187 Out of curiosity, what was your disk configuration?


I'm seeing atrocious speed in 2019 with both Storage Spaces with Parity, and RAID 5. It's up to 10x slower than 2016 with identical configuration.




Had the same problem with Server 2019.

After uninstalling the Defender-Service everything works as expected.



Have you tried disabled Receive Side Coalescing?  

"get-netdapaterrsc" will show you "True" where it's enabled and which NICs it's enabled on (if you have more than one).  Then you'll want to "Disable-NetAdapterRsc -Name *NameOftheNIC*"


I've seen significant performance improvement within my 2019 VM's with this disabled.

Hi @d3mon187

Were you ever able to figure out the solution for this Disk Performance issue in Windows 2019?




Has there been any updates on this?
I am having the same issue with my own server, 2019 seems to be about 3-5 times slower reading and writing data to disks with RAID1.
Removing Defender-Service and disabling Receive Side Coalescing, made no change.

Installing server 2016 on the same machine, and all RAID1 drives are back to the expected speed.


Just to test further I did also install two VM's with 2016 and 2019 on another machine with non raid drives, and both servers showed normal disk speed.

So it does seem like its a problem only on RAID drives, I do not currently have a machine with non raid drives to test the installation on, so can't test that.



Please try this 

Setting the "HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\MaxLazyWritePages" to HEX value of 2000  in Windows 2019

@haidongh can you provide any documentation on this registry value and why you think it might be needed on Win2019 vs 2016?

Seems like a change on how Windows 2019 handles lazy write pages. Check if setting the HEX value to 2000 instead of the default will improve the performance.
i have the same problem and adding that value to server 2022 didnt fix. server 2019 22 and vnext all are much slower.