vMotion : How reduce consumed memory after vmotion

Hi,

I have one virtual machine ( Total memory= 65GB,)

In FIRST hosts - Current Host memory Allocated is 15GB
After vMotion , the Host memory allocatted for the VM is increased to 58GB,

I just wants to know if any technique so that   after vMotion also the VM should get same Host memory allocation in Destination host.
kbjijoAsked:
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systechadminConsultantCommented:
have u configured DRS??
kbjijoAuthor Commented:
Yes, DRS . Even after DRS migration also  the host allocation memory increasing.
systechadminConsultantCommented:
its happening because of the DRS. Please review your DRS settings once and then try VMs.
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kbjijoAuthor Commented:
No, If i do manual migration also the same .
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
does it settle down and reduce, after 10 minutes.
kbjijoAuthor Commented:
yes, if wait for few  minutes, it is reducing, but not the host memory used before migration.

Explaining on this

VM conf with 65 GB

Before Migration : Host memory  allocatted is 5Gb
After migration : Host Memory allocatted is 58GB
after 10 Minutes, Host memory allocation reduced to 30GB

here problem like,
1 - In Highly utilized clusters, its hard to do migration, if DRS taken, then we can see hosts are touching to 99% usage
2 -  if we have 40% free on a host but, one or two VM migration will occupy the rest all...

How to control the host memory allocation to the VM during vMotion
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
So what is your actual issue ?
kbjijoAuthor Commented:
I wants to reduce the spike on host allocation for VM during a vMotion. what was the host allocation memory before and after vMotion should be same. Means target host should not give more physical memory to the VM during migration.
Because in Highly utilized cluster now doing with manual migration for maintenance. This increase in Host allocation during vMotion is challenging and unable to take the host into maintenance.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
So you have a virtual machine which is configured with 64GB RAM ?
kbjijoAuthor Commented:
I have attached a screenshot, how VM Host memory allocation differ Before & After Migration.

Just wants to know if any way if we can reduce the Host Memory More allocation after vMotion
before-and-after-vMotion.jpg
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
this shows a 16GB machine. e.g. you have allocated a maximum size of 16GB to the VM, so the maximum amount of memory the VM can use is 16GB (plus worst case, a a MB (400MB) for the host).

and you have allocated a VM of 16GB, so the max size of the VM will be 16GB plus a few MB working space.

No, you cannot reduce the host memory. Are you capacity figures on Active or Consumed/Allocated  Memory ?

If you look at resource allocation, you will see what the worst case use is, in terms of memory for this VM, that should be your guide....as for memory required in hosts.

vMotion can cause high cpu, and high memory in both host and VM, this is why large VMs, or busy VMs, e.g. Citrix Servers, Application Servers, are "pinned" disabled for DRS....(vMotion).

You do have VMware Tools installed ?

and which version of VMware vSphere ?

what function is the VM performing?

and you have no memory reservations, or shares defined ?
gheistCommented:
It is very crazy to allow virtual machine to consume host RAM + a bit more.
It will never work at good preformance (it will get hell slow once it fills all that RAM)
Just reduce VM size to   16GB (right where balooning pushed it back) and live happy.
kbjijoAuthor Commented:
You do have VMware Tools installed ?

Its uptodated, noticed its not the facts

and which version of VMware vSphere ?.

ESXi 5.5, even similar faced on 4.1 & 5.1. Its manageable on 3.5 & 4.1. as  not seen much this issue.

what function is the VM performing?
Not sure, have deal with many VMs.. , so confused still not getting a common fact .. to reduce while performing on high utilized clusters.

and you have no memory reservations, or shares defined ?
No reservation. it is in normal scenario
kbjijoAuthor Commented:
My doubt is as simple
"vMotion can cause high cpu, and high memory in both host and VM"

How can we reduce this during vMotion
kbjijoAuthor Commented:
this shows a 16GB machine. e.g. you have allocated a maximum size of 16GB to the VM, so the maximum amount of memory the VM can use is 16GB (plus worst case, a a MB (400MB) for the host).

The VM doesnt required its full amount from Physical RAM of ESX as dont hav ethat much demands... Its TRUE so that current host  given that much memory based on demand.
But once once it involved in migration, the new host providing it MAX even there is no demands

Here is the confusion and entirely effecting on capacity requirement.
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
You cannot, the high CPU and Memory, will only be for moments, until it settles.

if it is impacting service on the VM, disable it for vMotion.

we spent the afternoon looking at CPU and Memory, of VMs as they are vMotion around our large clusters, DRS is enabled, and there are some VMs, that do increase slightly, in terms of memory usage, but this does not exceed the Total Memory Allocated to the VM, so is not an issue. (which is Consumed Host Memory).

So have you oversubscribbed your VMs Memory, so if ALL VMs use the memory they have been allocated (in Edit Settings), does this figure exceed the memory in the Host ?

We ensure, that ALL the VMs memory total does not exceed the Host Memory. (worst case!)

e.g. a server with 128GB, we have 30 Machines allocated in VM settings 4GB each.

Worst case is always going to be 120GB for VMs, leaving 8GB for host!

vMoton event, will cause memory to increase, but not more, that it's worst case estimate,

We always work on worst case scenario, e.g. power on ALL VMs at once, ALL will demand max memory allocated, until they startup, and init, and then it wll fall off)
kbjijoAuthor Commented:
I can understand .. challenges during maintenance window as ended on cancel the change due to this.

if a cluster with 3 Host ( Only example), 3 hosts are currently 50% used, when involving on vMotion .. then it grows to approx of may 80, 90, 95.. even 99

How: One vm with 100Gb RAM , currently HOST MEM Util is only 10GB ( As demands) .. but after migration may it goes to 90/80/ even touch on 100. i
it will reduce after some moment/ may be hours but its more than the demands.

Actually the  VM doesn't needed the amount of MEM  from Physically, but ESX grant it after migration process . Here the "MIGRATION PROCESS " is culprit.... its making additional load on cluster.

If any Advance- migration variable available of ESXi to control this
kbjijoAuthor Commented:
We ensure, that ALL the VMs memory total does not exceed the Host Memory. (worst case!)

Absolutely, yes, issue is there , we have over committed cluetres and we have to stick on that as no other way. Looking how to rectify this .

But from the MIGRATION PROCESS, its sense less that  New ESXi is allocating MAX resource if that host free....
If the host is not free, initially it will allocate to MAX possible and reduce suddenly. In the moment of MAX allocate  ( May few Minutes) .... will touch to 99/100 marks and Host went Offline. Experienced it
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
This is the danger if you overcommit resources.

Reduce the memory in the VMs, if the VMs are never using the resources, look at max active memory, and reduce to these figures with a margin.

and then vMotion cannot go above the defined VM Memory allocated in the settings.

if you find when you have reduced and squeezed VM memoy, e.g. reduced you have performance issues with the VM, you need more memory in the VM, and Host.

or disable DRS.

Yes, if your overcommit on memory, e.g. 100%, hosts will start to fail....
kbjijoAuthor Commented:
yes  agree.. we dont have option as this customer agree.  So cancel of activity as we have excuse.


But apart of that if  considering migration process....
     
 
I  cant take the real experience as  sense

Cluster usage is only  44%( in two host) for a year
  -     > few big ram VM ( 65GB Vms only have host allocation is 5-10 GB), hence the Util is 40-50 %

Even DRS involvemnt not much increased as rarely VMs are migarting bcz of resources available for the VMs in both host. ( Agreed that VMs are over provisioned)


But i had canceled the change : because i cant take  one host ( Out of two) to maintennace due to Util.
--> the target host touched to 95 + %
--> (  memory allocation perspective) 10 GB  became 50+ for the VMs ... few of them are 40+ for few days and max reduced to  20- 30 GB


So cant sense it, if VM don't have demands in a year ( real time exper) .. just a vMotion made cluster un balanced,,,??
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Reduce the memory allocated to your VMs. (if they never use it!)

Bounced to VMware Support, they may know of a workaround.
gheistCommented:
65GB VMs do not fit in 65GB hosts - UNDERSTOOD? Your customer is dumbass, not you discharging your confusion on us.

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