Windows 10 hard disk in guest is extremely slow

[ozz-project]

Hello all,

I am currently trying to get a Windows 10 machine running with PVE. Unfortunately, writing in the VM is so slow that it is impossible to work with it. The write test under the host easily brings 50 Mb/s while in the VM I don't get over 4 MB/s.
I have installed the VM according to the defaults and made a lot of other attempts.

* Install Balloon driver but do not activate it
* NUMA activated
* Disk image is in RAW format
* Cache set to none (not the default none)
* async io enabled
* Windows high performance (power plan)
* swaping on different values (host)
* VirtIO Scsi controller (and also single)
* latest driver for Windows X.1.208

So far this has done nothing. Does anyone have another idea?

 

[dcsapak]

can you post some more info about your storage configuration? (disks/format/filesystem/etc. )?

 

[ozz-project]

I use a 5 TB as storage ST5000LM000-2AN170. (LVM-thin)
The os in on SAMSUNG MZVLB512HBJQ-00A00

CPU: 12 x Intel(R) Core(TM) i7-10710U CPU
RAM 64 GB

 

[dcsapak]

Ok the disk is an SMR one, which are known to be slower in some write/read pattern... In general, I would not recommend using SMR drives on PVE.

 

[Dunuin]

Jep, SMR is really terrible. I've got a Seagate SMR drive in a bare metal Windows and removed it because writing bigger files to it made the complete host unresponsive. That drive started fast with 180 MB/s and 20ms resonse time and after writing 30GB of big sequential writes it performance droped down to below 100kb/s with a average resopnse time of over 1 minute. 1 or 2 hours after the write was complete the host got responsive again and disk performance normalized...
I first thought that drive was damaged but after researching I found out that the drives used SMR and that this is normal behavior for that model...
SMR is basically like a QLC SSD where the write performance drops to very terrible values as soon as the cache has filled up.

Will never buy a SMR again...

 

[ozz-project]

Are the some other options than replacing the smr drive?

 

[itNGO]

Hi,
might be an option to set write back cache for the VM to dirty. But there is a risk of data loss when VM or Host crashes.
Also don't expect light speed. An SMR is not build for large sequential writing and will never be. You can hide the problem by using ZFS which its large default cache of 50% of RAM. But even then, there are limits....