[GitHub] [cloudstack] svenvogel edited a comment on issue #3319: Use virtio for platform emulator strings starting with Windows*

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svenvogel edited a comment on issue #3319: Use virtio for platform emulator 
strings starting with Windows*
URL: https://github.com/apache/cloudstack/pull/3319#issuecomment-491415223
 
 
   @skattoju4 @ustcweizhou @syed i will try to explain it.
   
   > @ustcweizhou the thinking behind always setting the root disk to ide was 
to be able to boot a windows vm regardless of whether or not virtio drivers 
were installed. That said setting all disks to virtio when selecting "Windows 
PV" when registering the template is one way to move forward. 
   
   first i have to say is yes! let me explain. as written in #3089 we have 
"NOT" only the problem with template! 
   @DennisKonrad wrote:
   
   When we select "Windows Server 2016 (64-bit)" as OS Type for an **W2K16 cd 
image** the resulting
   VMs will not start with multiple disks attached. This is due to the usage of 
multiple IDE interfaces in the VM description XML.
   
   1. we create a machine with "Windows Server 2016 (64-bit)" we have **one** 
disk with type root "ide". 
   <img width="433" alt="Bildschirmfoto 2019-05-10 um 21 50 40" 
src="https://user-images.githubusercontent.com/5433844/57553232-53245e80-736e-11e9-8a70-8221a88c1c7a.png";>
   2. after that we add **two more data disks** and those should "NOT" be IDE 
because QEMU dont like this! When we use NFS the second and third disk will be 
a "virtio" disk automatically.
   
   this pr should "NOT" remove/break or add functionality. 
   
   it should enable the normal functionality for managed storage according to 
NFS works and it is needed by QEMU if we choose "Windows Server 201X..." as OS 
Type. it is a bug that will affect only managed storage (as far as i i know). 
If any user wants "ONLY" virtio driver he can choose "other pv ..." OS Type.
   <img width="431" alt="Bildschirmfoto 2019-05-10 um 21 58 11" 
src="https://user-images.githubusercontent.com/5433844/57553489-f7a6a080-736e-11e9-892e-b703a076d576.png";>
   
   there is no discussion about performance of IDE or move all Microsoft 
Windows OS Types to virtio. it should be clear for everybody here that virtio 
is faster than ide and yes we dont need a driver for the root disk. but this 
content is not part of this discussion here.
   
   i hope it is more clear now?

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