vSphere and the isolation adress

Posted on 2010-11-29
Medium Priority
Last Modified: 2012-05-10
We had network problems yesterday and our 2 host ESX cluster couldn't see the default gateway, so (this is what i think anyway) HA was activated and things got in a right state. The gateway was down for a while and and we then couldn't start VMs due to "insufficient resources to satisfy configured failover level for HA."

Why does vSphere activate HA when it can't see the default gateway, I guess there's some logic behind but i can't figure out why?   That's the question.

Question by:kswan_expert
LVL 14

Accepted Solution

Deepak Kosaraju earned 1200 total points
ID: 34233718
To avoid this, you create an advanced parameter by clicking the advanced tab in HA settings and then enter das.isolationaddress and set the value to a pingable IP address you deem fit to serve as the IP address used by the HA cluster to determine whether or not the host has become isolated from the network.  YOu then create another parameter call das.usedefaultisolationaddress and set a value of FALSE.  You can a couple of IPs using this method, but if you do you should also increase the timeout value, this is das.failuredetectiontime, the default is 15 seconds, increase it to 30 seconds when more than 1 isolation address is used.  Refer to your ESX 3.5 resource management pdf, I've attached it for you.

Author Comment

ID: 34233996
Cheers for speedy reply!   We've set "dasiolation host = false" for the Cluster HA which apparently should fix the problem.  
We've made this change but are still wondering why HA is activated if it can't see the GW??
There's obviously some reason\logic behind it and now that we've disabled the feature will it have unexpected consequnces??


Assisted Solution

Virtalicious earned 400 total points
ID: 34234340
The underlying reason is that the guests may be in a dual brained mode in which it tries to run on multiple machines.  It engages HA to take ownership and ensure the guest is only run in one location.

The Theory being that although network is compromised the SAN may not be.

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Expert Comment

ID: 34248000
Hi kswan_expert,

HA will only try and contact the default gateway if it is unable to communicate with the other hosts. This is it's isolation check. You can change the address it checks for isolation but if the gateway goes down HA won't start, your host have to lose connection to each other.

Hope this helps.  

Author Comment

ID: 34254414
Cheers guys, humour me here but Vmware have set me wrong so I want to be 100% we get this right.

We set the HA advanced option to "dasiolation host = false"  as advised by a Vmware tech but this ain't worked!  We lost access to the GW again last night, HA failed on a host wouldn't restart and we received the message "Host ******* could not reach isolation address: #.#.#.#"

So, if i set the following for HA advanced options will it fix our probs

das.usedefaultisolationaddress = false

Do we have to set  a value for “dasiolation host” what happens if we don’t?  What do people usually use for these values.  I was thinking of using a local physical 2003 DC and a physical  file server that it pretty much never rebooted.

Assisted Solution

ianmellor earned 400 total points
ID: 34255283

I have never seen the advanced option "dasiolation host = false" , I think you mean the below setting.

das.usedefaultisolationaddress = <value>

This option/value pair disables the use of the default gateway as an isolation address, where <value> is either true or false. By default this value is set to true. This parameter is generally used in conjunction with the das.isolationaddress1 to das.isolationaddress10 parameter(s) listed below.

das.isolationaddress1 to das.isolationaddress10 = <value>

These option/value pair(s) specify more than one alternate isolation address for VMware HA to use, where <value> represents the IP address to be used for isolation detection. When using more than one isolation address it is recommended that the das.failuredetectiontime parameter be increased to ensure proper failover detection can occur. Also, although up to 10 different isolation addresses can be specified one or two addresses should be sufficient for proper failover detection

das.failuredetectiontime = <value>

This option/value pair changes the default failure detection timeout, where <value> represents the failure time in milliseconds. VMware HA uses this timeout in declaring an isolation response, and does not declare a host as isolated until this timeout has been reached without any heartbeats received. By default the default failure detection time is 15 seconds (15000 ms). However, another common alternative is 60 seconds (60000 ms).

Hope this helps you.

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