bas000m
Contributor
Contributor

2 Host HA-DRS cluster

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Hi All,

I have 2 hosts HA-DRS cluster, it seems that the DRS not work probably, when i look to the performance at 2 hosts, one of these hosts consume more memory 42 GB from 45 GB and the other one consume 26 GB of 45 GB, all of i know that the DRS balance the load on two host and automaticly migrate the VMs from one host to the other one,, but on my enviroment NOT ,,, any idea a bout this issue ???.

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vGuy
Expert
Expert

Well you could increase the migration threshold to max (which will directly impact the target load deviation) to enable DRS to vMotion off the VMs even for slight performance increase. Secondly, you can also look at this advanced setting to limit the no. of VMs per host, for vSphere 5.1 only:

http://www.yellow-bricks.com/2012/10/01/limit-the-amount-of-eggs-in-a-single-basket/

But I would not recommend any of the above actions unless your users are complaining about the performance. I would trust DRS to take the corrective if contention does arise.

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sparrowangelste
Virtuoso
Virtuoso

do you have DRS setup as manual mode?

--------------------- Sparrowangelstechnology : Vmware lover http://sparrowangelstechnology.blogspot.com
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bas000m
Contributor
Contributor

No, its fully automated mode .

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a_p_
Leadership
Leadership

No, DRS does not balance the workload. What DRS does is to migrate workloads in case of contention. It always does a cost-risk analysis before migrating VMs and if there's no need to do it, it won't generate any recommendations.

Here's an interesing blog post to read: http://www.yellow-bricks.com/drs-deepdive/

André

bas000m
Contributor
Contributor

Thanks for your replay, in this case what shall i do du to the heavy load on one host and the other host engough memory to handle load ,,, please find my current DRS settings :

Migration Automation Level : Fully Automated .

Power Management : Off.

DRS Recomandation : 0.

DRS Faults : 0

Migration Thershold : Apply priority 1, Priority 2, and Priority 3 recommendations.

Target Host load standard deviation <`=0.2

Current Host load standard devition 0.074 (Load Balanced ) .

Should i change the Migration Thershold to do Migration ???? Please advise .

Any help will be appreciated .

Thanks in advance ,

Basem

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jklick
Enthusiast
Enthusiast

What you've described can be a normal scenario in a VMware environment. Are you encountering performance issues of some sort? In a situation where the heavily utitlized host attempts to use more memory, one of several things can happen (none of which will normally cause a noticeable performance impact):

  • Host 1 will vMotion a VM to Host 2
  • Host 1 will invoke transparent page sharing to deduplicate memory pages that are being consumed
  • Host 1 will cause some unused/idle memory pages to be "ballooned" out from the VMs that are not using them anymore and redistribute as necessary.

If this is still concerning, you could try manually vMotioning off of Host 1 to balance things out better.

Also, if you have HA enabled on this cluster, another concern might be if you have enough memory capacity for your HA to work effectively.

Let us know if this helps or if you have further questions.

@JonathanKlick | www.vkernel.com
vGuy
Expert
Expert

Well you could increase the migration threshold to max (which will directly impact the target load deviation) to enable DRS to vMotion off the VMs even for slight performance increase. Secondly, you can also look at this advanced setting to limit the no. of VMs per host, for vSphere 5.1 only:

http://www.yellow-bricks.com/2012/10/01/limit-the-amount-of-eggs-in-a-single-basket/

But I would not recommend any of the above actions unless your users are complaining about the performance. I would trust DRS to take the corrective if contention does arise.

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a_p_
Leadership
Leadership
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depping
Leadership
Leadership

thanks for the links Smiley Happy

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