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RUG201110141
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inquiry about slot sizes and ESXi 4 and ESX 4 classic

I was looking to set the following HA advanced option settings:

das.slotCpuInMHz

das.slotMemInMB

The reason why is becuase I'm not using reservations in a couple of clusters of ESX hosts but I don't want the default slot size to be used. So I have a cluster of ESXi4 hosts and went into the advanced options of HA and set these settings and when I go under advanced runtime info on the summary tab of the cluster the the slots have clearly changed. When I attempt to do the same process on an ESX 4 classic cluster, by adding in the settings to the advanced options of HA nothing changes in the advanced runtime info. It's like the settings don't work with ESX 4 classic. Do these features only work on ESXi 4 and not ESX 4 classic?

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AntonVZhbankov
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You can modify slot sizes, but be careful with these settings. Think twice before modifying, and don't set too low memory level.

Here is very good detailed explanation how it works: http://www.yellow-bricks.com/vmware-high-availability-deepdiv/


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MCSA, MCTS, VCP, VMware vExpert '2009

http://blog.vadmin.ru

EMCCAe, HPE ASE, MCITP: SA+VA, VCP 3/4/5, VMware vExpert XO (14 stars)
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RParker
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First, these settings should not be changed. If they are changed, should only be at the guidance of VM Ware Support.

If they instructed you to change them, they should be able to assist in the changes.

So where do you find these settings should be changed for HA? And what will changing them do.. because if you are changing them as a result of reading them on a website, it was probably something specific and shouldn't be assumed to work for every HA.

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RUG201110141
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wow that's not very helpful.

1) these settings are documented in vmware documentation for the product

2) I'm not reading some random webiste I'm reading the vmware documentation and it doesn't apparently mention that I have to call VMware support to use these settings.

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Troy_Clavell
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i don't agree with adding these setting in, period. All it is doing is telling your cluster you have more slots available then is actually calculated by VMware's conservative HA failover capacity calculations.

I would much rather just disable admission control, but that is my opinion.

As far as the settings, they should be enabled on the cluster. You may have to break HA, then enable HA again after you have changed the advanced settings.

More here:

http://www.vmware.com/pdf/vsphere4/r40/vsp_40_availability.pdf

http://www.yellow-bricks.com/vmware-high-availability-deepdiv/

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RParker
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> apparently mention that I have to call VMware support to use these settings.

I didn't say you had to ask permission, mr. paranoid, I simply asked if you understood what they were FOR.

If you want to go mucking with your advianced settings, be my guest. you read it on VM Ware site, that's fine. But if you change something knowing the impact, you will be doing yourself wrong.

So if you change them, and it doesn't work, that's one thing. If you change them and it's not going to fix your problem that is something else.

> wow that's not very helpful.

It is when you look at the context that you realize this is a USER forum, someone might be under the mistaken impression that these are general settings, and should be changed on a whim. So if NEED to change them, I was merely prompting to ensure you know what you are getting yourself into.

Because changing a setting just because its there isn't very safe. Someone else may see this as a new undocumented feature, and I was trying to understand why you needed to change this in the first place.

and I see you dodged that question, so it must mean you trying to "tweak" something and not fully understand the impact. Some settings require other settings to be set, before they can be changed as well.. so what you deem as "... not very helpful." may actually be helpful when you know the situation.

you are welcome.

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AntonVZhbankov
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>First, these settings should not be changed.

I'm absolutely not agree with this statement. I have 40+ VMs in my production cluster, and 2 of them have very high memory reservation settings (2 GB) due to application requirements. So my slot size without manual correction would become about 2.5GB and HA will think that cluster with plenty of free memory (3 * 32 GB) seriously lacks resources.

So, I would correct this statement to "These settings should not be changed unless you are absolutely sure it's required and you fully understand where it would lead".


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MCSA, MCTS, VCP, VMware vExpert '2009

http://blog.vadmin.ru

EMCCAe, HPE ASE, MCITP: SA+VA, VCP 3/4/5, VMware vExpert XO (14 stars)
VMUG Russia Leader
http://t.me/beerpanda
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RUG201110141
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I guess I'm in a slightly similar situation. We are beginning to virtualize SAP systems and SAP's best practice doc for virtualizing SAP is to use reservations. These SAP vm's are significantly beefier than the rest of the vm's in the cluster so it scews the slot size big time if I set those reservations.

Additionally, I don't like the default slot sizes that are setup. To me it gives an unrealistic view of the amount of available compute power remaining in the clusters where I am not using any form of reservations. I could be misreading what the Advanced Runtime Info provides I guess.

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AntonVZhbankov
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You can modify slot sizes, but be careful with these settings. Think twice before modifying, and don't set too low memory level.

Here is very good detailed explanation how it works: http://www.yellow-bricks.com/vmware-high-availability-deepdiv/


---

MCSA, MCTS, VCP, VMware vExpert '2009

http://blog.vadmin.ru

EMCCAe, HPE ASE, MCITP: SA+VA, VCP 3/4/5, VMware vExpert XO (14 stars)
VMUG Russia Leader
http://t.me/beerpanda
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braendi
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The memory value is actually called das.slotMemInMB this value is like a maximum value if the calculated values is not reaching the configured das.slotMemInMB value you see still the calculated value. Try to make a reservation and than you will see that the set value will be shown.

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RUG201110141
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That link is actually very helpful. Thanks a lot.

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