Network Failure

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
Abdul WahidAsked:
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Gareth Tomlinson CISSPNetwork and Security ManagerCommented:
Often this is because your domain controller is one of the VMs, and without it the services will not start.
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Abdul WahidAuthor Commented:
Gareth,

Well, the Domain controllers are located on physical machines not VMs.
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Gareth Tomlinson CISSPNetwork and Security ManagerCommented:
Hmm, not that then. What about the central management service for Xenserver, do you have one?
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Abdul WahidAuthor Commented:
Center Management Service mean? if you are talking about XenCenter yes i have.
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Gareth Tomlinson CISSPNetwork and Security ManagerCommented:
Is that physical, or a VM? HA depends on something managing the resources; my only experience is VMWare, unfortunately.
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Abdul WahidAuthor Commented:
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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joharderCommented:
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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eeRootCommented:
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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Abdul WahidAuthor Commented:
Yes  Joharder the storage was disconnected.....
eeroot yes the restart priority is configured and the server failure limit(2).
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Gerald ConnollyCommented:
What was the cause of your network failure?
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Abdul WahidAuthor Commented:
The Entire switches was done for a while.
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Gerald ConnollyCommented:
So what power failure?

if so dont you have your switches on a UPS?
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ArneLoviusCommented:
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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ArneLoviusCommented:
conciseness and completeness
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