[ovirt-users] About the vm memory limit

[Tommy Sway]

I would like to ask if there is any limit on the memory size of virtual
machines, or performance curve or something like that?

As long as there is memory on the physical machine, the more virtual
machines the better?

 

In our usage scenario, there are many virtual machines with databases, and
their memory varies greatly. 

For some virtual machines, 4G memory is enough, while for some virtual
machines, 64GB memory is needed.

 

I want to know what is the best use of memory for a virtual machine, since
the virtual machine is just a QEMU emulation process on a physical machine,
and I worry that it is not using as much memory as a physical machine.
Understand this so that we can develop guidelines for optimal memory usage
scenarios for virtual machines.

 

Thank you!

 

 

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[ovirt-users] Re: why cannot set the power management proxy server ?

[Tommy Sway]

I set lanplus=1, and then it ok.

 

What’s meaning of it ?

 

 

 

From: Strahil Nikolov  
Sent: Friday, September 24, 2021 3:13 AM
To: Tommy Sway 
Subject: Re: [ovirt-users] why cannot set the power management proxy server ?

 

Try adding 'lanplus=0' into the options.

 

Best Regards,

Strahil Nikolov

On Thu, Sep 23, 2021 at 5:59, Tommy Sway

mailto:sz_cui...@163.com> > wrote:

I can use ipmitool to send commands from any KVM host to other hosts in the 
same cluster. 

However, an internal error is reported when CONFIGURING power proxy on engine. 

 

How can I locate the fault?

 

 

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[ovirt-users] Re: VM hanging at sustained high throughput

[Shantur Rathore]

On Thu, Sep 23, 2021 at 8:20 PM Strahil Nikolov via Users
 wrote:
>
> What happens if you define a tmpfs and then create the qemu disk ontop of 
> that ramdisk.
> Does qemu hang again ?

It works fine. Cannot reproduce the issue

>
> Best Regards,
> Strahil Nikolov
>
> On Thu, Sep 23, 2021 at 18:25, Shantur Rathore
>  wrote:
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[ovirt-users] Re: Hosted Engine cluster version compatib.

[Diggy Mc]

The only VM that my cluster compatibility upgrade complains about is 
"HostedEngine".  I'm not about to test my SQL knowledge by writing my own SQL 
command and I see no reason to touch VMs that don't upset the cluster upgrade.  
Can you please provide a SQL command that corrects ONLY the HostedEngine VM ??? 
 Much appreciated.  NOTE: All my servers' OS (physical and VM) are set to 
"Etc/UCT" wherever possible.
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[ovirt-users] Re: VM hanging at sustained high throughput

[Strahil Nikolov via Users]

What happens if you define a tmpfs and then create the qemu disk ontop of that 
ramdisk.Does qemu hang again ?
Best Regards,Strahil Nikolov
 
 
  On Thu, Sep 23, 2021 at 18:25, Shantur Rathore 
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[ovirt-users] Re: Hosted Engine cluster version compatib.

[Michal Skrivanek]

> On 23. 9. 2021, at 19:35, Gianluca Cecchi  wrote:
> 
> On Thu, Sep 23, 2021 at 7:29 PM Diggy Mc  > wrote:
> I just upgraded the HE to 4.4.8.6 and rebooted it.  I still cannot upgrade 
> the cluster compatibility level.  Cannot edit properties of the HE either.
> 
> 
> If I understood correctly, the fix is in the sense that if not already 
> updated to 4.4.8, the flow should be ok now.

correct

> But probably to solve the problems for the guys that already updated to the 
> "broken" 4.4.8, more work still has to be done by the developers...

yeah, it can’t be fixed that easily once it happens. Probably time for direct 
database update….

Assuming that you don’t have VMs with different TZs then change all Windwos VMs 
to your local TZ(here EST) with
# /usr/share/ovirt-engine/dbscripts/engine-psql.sh -c "update vm_static SET 
time_zone='Eastern Standard Time' where os in 
('1','3','4','10','11','12','16','17','20','21','23','25','26','27','29','31')";

And also for all non-Windows VMs to 'Etc/GMT’  with
# /usr/share/ovirt-engine/dbscripts/engine-psql.sh -c "update vm_static SET 
time_zone='Etc/GMT' where os not in 
('1','3','4','10','11','12','16','17','20','21','23','25','26','27','29','31')”;

That will cover HostedEngine as well, and it should fix the CL update problem.

Caveat - I havent’ tried that and it’s not tested.
Doublecheck it has been set.
Zones should be from 
https://github.com/oVirt/ovirt-engine/blob/master/packaging/conf/timezones-defaults.properties

Hope it helps,
michal

> 
> Gianluca
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[ovirt-users] Re: about the power management of the hosts

[Strahil Nikolov via Users]

When systems go 'crazy' there is no guarantee that they will be completely 
unresponsive. HA VMs should be fine, but regular VMs won't be restarted as the 
engine won't know if the host is dead or not (and no fencing is configured to 
guarantee that).
Also, storage tasks could fail if that host is also the SPM.
Best Regards,Strahil Nikolov
 
 
  On Thu, Sep 23, 2021 at 3:09, Tommy Sway wrote:   
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[ovirt-users] Re: Hosted Engine cluster version compatib.

[Gianluca Cecchi]

On Thu, Sep 23, 2021 at 7:29 PM Diggy Mc  wrote:

> I just upgraded the HE to 4.4.8.6 and rebooted it.  I still cannot upgrade
> the cluster compatibility level.  Cannot edit properties of the HE either.
>
>
If I understood correctly, the fix is in the sense that if not already
updated to 4.4.8, the flow should be ok now.
But probably to solve the problems for the guys that already updated to the
"broken" 4.4.8, more work still has to be done by the developers...

Gianluca
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[ovirt-users] Re: Hosted Engine cluster version compatib.

[Diggy Mc]

I just upgraded the HE to 4.4.8.6 and rebooted it.  I still cannot upgrade the 
cluster compatibility level.  Cannot edit properties of the HE either.

Error I receive when trying to update the compatibility level:
Error while executing action: Cannot update cluster because the update 
triggered update of the VMs/Templates and it failed for the following: 
HostedEngine. To fix the issue, please go to each of them, edit, change the 
Custom Compatibility Version (or other fields changed previously in the cluster 
dialog) and press OK. If the save does not pass, fix the dialog validation. 
After successful cluster update, you can revert your Custom Compatibility 
Version change (or other changes). If the problem still persists, you may refer 
to the engine.log file for further details.

Error I receive when trying to edit the HE properties:
There was an attempt to change Hosted Engine VM values that are locked.

This is becoming very annoying.  Updating is an hours-long process in my 
environment and has now failed twice.
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[ovirt-users] Re: VM hanging at sustained high throughput

[Shantur Rathore]

I see the same issue in local scratch disk with scratchpad.
I think qemu should block the io rather than pausing the VM.

On Thu, Sep 23, 2021 at 4:06 PM David Johnson 
wrote:

> I replaced the SSD intent log drive with an NVME drive, and the system is
> much more stable now.
>
> *David Johnson*
> *Director of Development, Maxis Technology*
> 844.696.2947 ext 702 (o) | 479.531.3590 (c)
> 
> 
> 
>
> *Follow us:*  
>
>
> On Thu, May 27, 2021 at 5:57 PM David Johnson <
> djohn...@maxistechnology.com> wrote:
>
>> Hi ovirt gurus,
>>
>> This is an interesting issue, one I never expected to have.
>>
>> When I push high volumes of writes to my NAS, I will cause VM's to go
>> into a paused state. I'm looking at this from a number of angles, including
>> upgrades on the NAS appliance.
>>
>> I can reproduce this problem at will running a centos 7.9 VM on Ovirt 4.5.
>>
>> *Questions:*
>>
>> 1. Is my analysis of the failure (below) reasonable/correct?
>>
>> 2. What am I looking for to validate this?
>>
>> 3. Is there a configuration that I can set to make it a little more
>> robust while I acquire the hardware to improve the NAS?
>>
>>
>> *Reproduction:*
>>
>> Standard test of file write speed:
>>
>> [root@cen-79-pgsql-01 ~]# dd if=/dev/zero of=./test bs=512k count=4096
>> oflag=direct
>> 4096+0 records in
>> 4096+0 records out
>> 2147483648 bytes (2.1 GB) copied, 1.68431 s, 1.3 GB/s
>>
>>
>> Give it more data
>>
>> [root@cen-79-pgsql-01 ~]# dd if=/dev/zero of=./test bs=512k count=12228
>> oflag=direct
>> 12228+0 records in
>> 12228+0 records out
>> 6410993664 bytes (6.4 GB) copied, 7.22078 s, 888 MB/s
>>
>>
>> The odds are about 50/50 that 6 GB will kill the VM, but 100% when I hit
>> 8 GB.
>>
>> *Analysis:*
>>
>> What I think appears to be happening is that the intent cache on the NAS
>> is on an SSD, and my VM's are pushing data about three times as fast as the
>> SSD can handle. When the SSD gets queued up beyond a certain point, the NAS
>> (which places reliability over speed) says "Whoah Nellie!", and the VM
>> chokes.
>>
>>
>> *David Johnson*
>>
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[ovirt-users] Re: VM hanging at sustained high throughput

[David Johnson]

I replaced the SSD intent log drive with an NVME drive, and the system is
much more stable now.

*David Johnson*
*Director of Development, Maxis Technology*
844.696.2947 ext 702 (o) | 479.531.3590 (c)




*Follow us:*  


On Thu, May 27, 2021 at 5:57 PM David Johnson 
wrote:

> Hi ovirt gurus,
>
> This is an interesting issue, one I never expected to have.
>
> When I push high volumes of writes to my NAS, I will cause VM's to go into
> a paused state. I'm looking at this from a number of angles, including
> upgrades on the NAS appliance.
>
> I can reproduce this problem at will running a centos 7.9 VM on Ovirt 4.5.
>
> *Questions:*
>
> 1. Is my analysis of the failure (below) reasonable/correct?
>
> 2. What am I looking for to validate this?
>
> 3. Is there a configuration that I can set to make it a little more robust
> while I acquire the hardware to improve the NAS?
>
>
> *Reproduction:*
>
> Standard test of file write speed:
>
> [root@cen-79-pgsql-01 ~]# dd if=/dev/zero of=./test bs=512k count=4096
> oflag=direct
> 4096+0 records in
> 4096+0 records out
> 2147483648 bytes (2.1 GB) copied, 1.68431 s, 1.3 GB/s
>
>
> Give it more data
>
> [root@cen-79-pgsql-01 ~]# dd if=/dev/zero of=./test bs=512k count=12228
> oflag=direct
> 12228+0 records in
> 12228+0 records out
> 6410993664 bytes (6.4 GB) copied, 7.22078 s, 888 MB/s
>
>
> The odds are about 50/50 that 6 GB will kill the VM, but 100% when I hit 8
> GB.
>
> *Analysis:*
>
> What I think appears to be happening is that the intent cache on the NAS
> is on an SSD, and my VM's are pushing data about three times as fast as the
> SSD can handle. When the SSD gets queued up beyond a certain point, the NAS
> (which places reliability over speed) says "Whoah Nellie!", and the VM
> chokes.
>
>
> *David Johnson*
>
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[ovirt-users] oVirt 4.4.8 Async update #4

[Sandro Bonazzola]

oVirt 4.4.8 Async update #4

On September 23rd 2021 the oVirt project released an async update to the
following packages:

   -

   ovirt-engine 4.4.8.6

Fixing the following bugs:
Bug 2005221  - Cluster
compatibility version upgrade from 4.5 to 4.6

-- 

Sandro Bonazzola

MANAGER, SOFTWARE ENGINEERING, EMEA R RHV

Red Hat EMEA 

sbona...@redhat.com


*Red Hat respects your work life balance. Therefore there is no need to
answer this email out of your office hours.*
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[ovirt-users] Re: Sparse VMs from Templates - Storage issues

[Shantur Rathore]

So,
I did more digging and now I know how to reproduce it.
I created a VM and added a disk on local ssd using scratchpad hook,
formatted and mounted this scratchdisk.
Now, when I try to do heavy IO on this scratchdisk on local ssd, like,
dd if=/dev/zero of=/mnt/scratchdisk/test bs=1M count=1, qemu
pauses VM.
Debug logs in libvirt shows

2021-09-23 11:04:32.765+: 463319: debug : virThreadJobSet:94 :
Thread 463319 (rpc-worker) is now running job
remoteDispatchNodeGetFreePages
2021-09-23 11:04:32.765+: 463319: debug : virNodeGetFreePages:1614
: conn=0x7f8620018ba0, npages=3, pages=0x7f8670009960,
startCell=4294967295, cellCount=1, counts=0x7f8670007db0, flags=0x0
2021-09-23 11:04:32.765+: 463319: debug : virThreadJobClear:119 :
Thread 463319 (rpc-worker) finished job remoteDispatchNodeGetFreePages
with ret=0
2021-09-23 11:04:34.235+: 488774: debug :
qemuMonitorJSONIOProcessLine:220 : Line [{"timestamp": {"seconds":
1632395074, "microseconds": 235454}, "event": "BLOCK_IO_ERROR",
"data": {"device": "", "nospace": false, "node-name":
"libvirt-3-format", "reason": "Input/output error", "operation":
"write", "action": "stop"}}]
2021-09-23 11:04:34.235+: 488774: info :
qemuMonitorJSONIOProcessLine:235 : QEMU_MONITOR_RECV_EVENT:
mon=0x7f860c14b700 event={"timestamp": {"seconds": 1632395074,
"microseconds": 235454}, "event": "BLOCK_IO_ERROR", "data": {"device":
"", "nospace": false, "node-name": "libvirt-3-format", "reason":
"Input/output error", "operation": "write", "action": "stop"}}
2021-09-23 11:04:34.235+: 488774: debug :
qemuMonitorJSONIOProcessEvent:181 : mon=0x7f860c14b700
obj=0x7f860c0e7450
2021-09-23 11:04:34.235+: 488774: debug :
qemuMonitorEmitEvent:1166 : mon=0x7f860c14b700 event=BLOCK_IO_ERROR
2021-09-23 11:04:34.235+: 488774: debug :
qemuProcessHandleEvent:581 : vm=0x7f86201d6df0
2021-09-23 11:04:34.235+: 488774: debug : virObjectEventNew:624 :
obj=0x7f860c0d82f0
2021-09-23 11:04:34.235+: 488774: debug :
qemuMonitorJSONIOProcessEvent:206 : handle BLOCK_IO_ERROR
handler=0x7f8639c77a90 data=0x7f860c0661c0

To confirm the local ssd is fine, have enough space where scratch disk
is located and I could run dd in host without any issues.

This happens on other storages as well.
So this seems like an issue with qemu when heavy IO is happening on a disk.

On Thu, Sep 23, 2021 at 7:19 AM Tommy Sway  wrote:
>
> Another option with (still tech preview) is Managed Block Storage (Cinder 
> based storage).
>
> It still tech preview in 4.4 ??
>
>
>
>
>
>
>
> -Original Message-
> From: users-boun...@ovirt.org  On Behalf Of Nir 
> Soffer
> Sent: Wednesday, August 11, 2021 4:26 AM
> To: Shantur Rathore 
> Cc: users ; Roman Bednar 
> Subject: [ovirt-users] Re: Sparse VMs from Templates - Storage issues
>
> On Tue, Aug 10, 2021 at 4:24 PM Shantur Rathore  
> wrote:
> >
> > Hi all,
> >
> > I have a setup as detailed below
> >
> > - iSCSI Storage Domain
> > - Template with Thin QCOW2 disk
> > - Multiple VMs from Template with Thin disk
>
> Note that a single template disk used by many vms can become a performance 
> bottleneck, and is a single point of failure. Cloning the template when 
> creating vms avoids such issues.
>
> > oVirt Node 4.4.4
>
> 4.4.4 is old, you should upgrade to 4.4.7.
>
> > When the VMs boots up it downloads some data to it and that leads to 
> > increase in volume size.
> > I see that every few seconds the VM gets paused with
> >
> > "VM X has been paused due to no Storage space error."
> >
> >  and then after few seconds
> >
> > "VM X has recovered from paused back to up"
>
> This is normal operation when a vm writes too quickly and oVirt cannot extend 
> the disk quick enough. To mitigate this, you can increase the volume chunk 
> size.
>
> Created this configuration drop in file:
>
> # cat /etc/vdsm/vdsm.conf.d/99-local.conf
> [irs]
> volume_utilization_percent = 25
> volume_utilization_chunk_mb = 2048
>
> And restart vdsm.
>
> With this setting, when free space in a disk is 1.5g, the disk will be 
> extended by 2g. With the default setting, when free space is 0.5g the disk 
> was extended by 1g.
>
> If this does not eliminate the pauses, try a larger chunk size like 4096.
>
> > Sometimes after a many pause and recovery the VM dies with
> >
> > "VM X is down with error. Exit message: Lost connection with qemu process."
>
> This means qemu has crashed. You can find more info in the vm log at:
> /var/log/libvirt/qemu/vm-name.log
>
> We know about bugs in qemu that cause such crashes when vm disk is extended. 
> I think the latest bug was fixed in 4.4.6, so upgrading to 4.4.7 will fix 
> this issue.
>
> Even with these settings, if you have a very bursty io in the vm, it may 
> become paused. The only way to completely avoid these pauses is to use a 
> preallocated disk, or use file storage (e.g. NFS). Preallocated disk can be 
> thin provisioned on the server side so it does not mean you need more 
> storage, but you will not be able to use shared 

[ovirt-users] Re: Sparse VMs from Templates - Storage issues

[Tommy Sway]

Another option with (still tech preview) is Managed Block Storage (Cinder based 
storage).

It still tech preview in 4.4 ??







-Original Message-
From: users-boun...@ovirt.org  On Behalf Of Nir Soffer
Sent: Wednesday, August 11, 2021 4:26 AM
To: Shantur Rathore 
Cc: users ; Roman Bednar 
Subject: [ovirt-users] Re: Sparse VMs from Templates - Storage issues

On Tue, Aug 10, 2021 at 4:24 PM Shantur Rathore  
wrote:
>
> Hi all,
>
> I have a setup as detailed below
>
> - iSCSI Storage Domain
> - Template with Thin QCOW2 disk
> - Multiple VMs from Template with Thin disk

Note that a single template disk used by many vms can become a performance 
bottleneck, and is a single point of failure. Cloning the template when 
creating vms avoids such issues.

> oVirt Node 4.4.4

4.4.4 is old, you should upgrade to 4.4.7.

> When the VMs boots up it downloads some data to it and that leads to increase 
> in volume size.
> I see that every few seconds the VM gets paused with
>
> "VM X has been paused due to no Storage space error."
>
>  and then after few seconds
>
> "VM X has recovered from paused back to up"

This is normal operation when a vm writes too quickly and oVirt cannot extend 
the disk quick enough. To mitigate this, you can increase the volume chunk size.

Created this configuration drop in file:

# cat /etc/vdsm/vdsm.conf.d/99-local.conf
[irs]
volume_utilization_percent = 25
volume_utilization_chunk_mb = 2048

And restart vdsm.

With this setting, when free space in a disk is 1.5g, the disk will be extended 
by 2g. With the default setting, when free space is 0.5g the disk was extended 
by 1g.

If this does not eliminate the pauses, try a larger chunk size like 4096.

> Sometimes after a many pause and recovery the VM dies with
>
> "VM X is down with error. Exit message: Lost connection with qemu process."

This means qemu has crashed. You can find more info in the vm log at:
/var/log/libvirt/qemu/vm-name.log

We know about bugs in qemu that cause such crashes when vm disk is extended. I 
think the latest bug was fixed in 4.4.6, so upgrading to 4.4.7 will fix this 
issue.

Even with these settings, if you have a very bursty io in the vm, it may become 
paused. The only way to completely avoid these pauses is to use a preallocated 
disk, or use file storage (e.g. NFS). Preallocated disk can be thin provisioned 
on the server side so it does not mean you need more storage, but you will not 
be able to use shared templates in the way you use them now. You can create vm 
from template, but the template is cloned to the new vm.

Another option with (still tech preview) is Managed Block Storage (Cinder based 
storage). If your storage server is supported by Cinder, we can managed it 
using cinderlib. In this setup every disk is a LUN, which may be thin 
provisioned on the storage server. This can also offload storage operations to 
the server, like cloning disks, which may be much faster and more efficient.

Nir
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