VM Performance after Template Upload

[Mevludin Blazevic <mb...@uni-koblenz.de>]

Hi all,

some of our users have reported that after they uploaded QCOW2 templates 
to our ACS environment and started a VM from the template, the VMs ran 
very slow. In contrast, VMs installed directly in ACS using ISOs for 
example are very fast. I wonder if something in the upload view was 
misconfigured by the users.

We are using KVM and in the upload view we can choose Root disk 
controller, OS Type and other options like enabling HVM. Any ideas?

Best Regards

Mevludin

Re: VM Performance after Template Upload

[Mevludin Blazevic <mb...@uni-koblenz.de>]

Hi,

using ACS with KVM and RBD/Ceph, it turns out that the user has chosed a 
Compute Offering with volume type "Fat" provisioned. After he reinstall 
the VM from the template using a Compute Offering with Volume "thin" 
provisioned, the performance level was as high as the other VMs. Seems 
like there is a huge performance difference between fat and thin, 
however, I have not tested out the "sparse" option. I always thought 
using RBD as primary storage there is no difference between fat and thin...

Regards,

Mevludin

Am 07.09.2022 um 15:01 schrieb Nux:
> Hi,
>
> Check that the templates were registered with the appropriate profiles 
> (ie of type CentOS7 etc), particularly if their storage and network 
> devices are Virtio ones.
> You can do this with lspci on Linux - inside the VM - ethernet and 
> storage should present themselves as "virtio" or similar.
>
> Another thing you can look at, is whether the qcow2 file they upload 
> is funky in any way, ie look at compat, cluster_size and compare with 
> a file in your cloud that you know works well. You can use "qemu-img 
> info file.qcow2" for this.
>
> hth
>
> ---
> Nux
> www.nux.ro
>
> On 2022-09-07 13:26, Mevludin Blazevic wrote:
>> Hi all,
>>
>> some of our users have reported that after they uploaded QCOW2
>> templates to our ACS environment and started a VM from the template,
>> the VMs ran very slow. In contrast, VMs installed directly in ACS
>> using ISOs for example are very fast. I wonder if something in the
>> upload view was misconfigured by the users.
>>
>> We are using KVM and in the upload view we can choose Root disk
>> controller, OS Type and other options like enabling HVM. Any ideas?
>>
>> Best Regards
>>
>> Mevludin 

Re: VM Performance after Template Upload

[Nux <nu...@li.nux.ro>]

Hi,

Check that the templates were registered with the appropriate profiles 
(ie of type CentOS7 etc), particularly if their storage and network 
devices are Virtio ones.
You can do this with lspci on Linux - inside the VM - ethernet and 
storage should present themselves as "virtio" or similar.

Another thing you can look at, is whether the qcow2 file they upload is 
funky in any way, ie look at compat, cluster_size and compare with a 
file in your cloud that you know works well. You can use "qemu-img info 
file.qcow2" for this.

hth

---
Nux
www.nux.ro

On 2022-09-07 13:26, Mevludin Blazevic wrote:
> Hi all,
> 
> some of our users have reported that after they uploaded QCOW2
> templates to our ACS environment and started a VM from the template,
> the VMs ran very slow. In contrast, VMs installed directly in ACS
> using ISOs for example are very fast. I wonder if something in the
> upload view was misconfigured by the users.
> 
> We are using KVM and in the upload view we can choose Root disk
> controller, OS Type and other options like enabling HVM. Any ideas?
> 
> Best Regards
> 
> Mevludin

Re: VM Performance after Template Upload

[Ivan Kudryavtsev <iv...@bw-sw.com>]

Hi, the qcow2 volumes may be thin, sparse, full. Maybe the fs is slow, so
while the image does cow allocations, the performance degrades? Try to make
a full qcow2 image by:

qemu-img create -o preallocation=full -f qcow2

And check again.


ср, 7 сент. 2022 г., 16:26 Mevludin Blazevic <mb...@uni-koblenz.de>:

> Hi all,
>
> some of our users have reported that after they uploaded QCOW2 templates
> to our ACS environment and started a VM from the template, the VMs ran
> very slow. In contrast, VMs installed directly in ACS using ISOs for
> example are very fast. I wonder if something in the upload view was
> misconfigured by the users.
>
> We are using KVM and in the upload view we can choose Root disk
> controller, OS Type and other options like enabling HVM. Any ideas?
>
> Best Regards
>
> Mevludin
>
>