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Network Failure

Posted on 2016-08-18
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Last Modified: 2016-09-11
We have five xenserver host machines which has around 20 VMs last night we had a network failure all host machines were disconnected from switch where they stop connection with share storage, later once we recovered the connectivity found most of the VMs were turned off, none of them  turned on automatically(HA is enabled), can you please share your ideas on the same.

for me this was because of no host available at that time to restart VMs themselves somewhere in other physical machine so that could be the reason that they went off.

Regards
Abdul
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Question by:Abdul Wahid
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14 Comments
 
LVL 5

Expert Comment

by:Gareth Tomlinson CISSP
ID: 41762279
Often this is because your domain controller is one of the VMs, and without it the services will not start.
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Author Comment

by:Abdul Wahid
ID: 41762459
Gareth,

Well, the Domain controllers are located on physical machines not VMs.
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Expert Comment

by:Gareth Tomlinson CISSP
ID: 41762470
Hmm, not that then. What about the central management service for Xenserver, do you have one?
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Author Comment

by:Abdul Wahid
ID: 41762713
Center Management Service mean? if you are talking about XenCenter yes i have.
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Expert Comment

by:Gareth Tomlinson CISSP
ID: 41762751
Is that physical, or a VM? HA depends on something managing the resources; my only experience is VMWare, unfortunately.
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Author Comment

by:Abdul Wahid
ID: 41762959
yes but here the reason is that all resources were disconnected, i hope someone from citrix will reply.. Thank you sir.
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LVL 15

Assisted Solution

by:joharder
joharder earned 125 total points (awarded by participants)
ID: 41763159
If I understand the scenario, storage was inaccessible as well.  If XenServer can't access storage, it can't boot VMs.
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LVL 22

Assisted Solution

by:eeRoot
eeRoot earned 125 total points (awarded by participants)
ID: 41764539
HA will handle fail over if there is a host to fail over to.  But if all hosts and storage are offline, it may have not been able to trigger a restart.  Ceck your HA restart priority and "server failure limit" settings.  Make sure that the VM's are listed in the restart priority list.  And if the "server failure limit" it too low, it may block restarts.
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Author Comment

by:Abdul Wahid
ID: 41764638
Yes  Joharder the storage was disconnected.....
eeroot yes the restart priority is configured and the server failure limit(2).
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LVL 17

Expert Comment

by:Gerald Connolly
ID: 41764691
What was the cause of your network failure?
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Author Comment

by:Abdul Wahid
ID: 41765280
The Entire switches was done for a while.
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Expert Comment

by:Gerald Connolly
ID: 41766503
So what power failure?

if so dont you have your switches on a UPS?
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Accepted Solution

by:
ArneLovius earned 250 total points (awarded by participants)
ID: 41766635
There are some Hyper-V topologies that will fail to start if there is no AD DC available, but XenServer does not require an AD DC for VMs to start,

If the XenServer storage was connected over iSCSI, then teh storage woudl have been forcibly disconnected from XenServer, this would be the probable cause of the VMs failing to start when the network outage was remediated.

It is probable that the VMs would have auto started if the XenServer hosts were restarted after the network outage had been remediated.
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Expert Comment

by:ArneLovius
ID: 41793205
conciseness and completeness
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