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During live migration, instance is not able to ping or ssh

asked 2016-09-13 06:08:43 -0500

manas-biswal06 gravatar image

We have a set up with one controller node and two compute node. We are using OVS + VXLAN Everything is running fine. While doing block live migration, machine got migrated to another compute but it stops pinging ( through private ip and floating ip)

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answered 2016-09-13 12:05:47 -0500

fifi gravatar image

updated 2016-09-13 12:10:41 -0500

I read some where that when block live migration starts in openstack, it does not respond to any outside request. However, I don't think its true. It can be true just after stop&copy phase starts.

I also faced the same problem. To measure migration downtime, I used ping, but I start pinging the vm just before starting block migration. Ping gets interrupted for a while but continue normally untill the end of migration. To get better results, you'd better decrease the intervals between each ping request. In my case, I ping like sudo ping -i 0.01 192.168.0.1

For ssh, you're right. Even if you set up a ssh connection before migration, it gets interrupted during the migration. By the way, there is no difference between private or floating IPs in this matter.

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In our case, while live migration, we can able to ping, but after few ping ( 3 to 4) ping stops permanently.

manas-biswal06 gravatar imagemanas-biswal06 ( 2016-09-14 00:08:31 -0500 )edit

If i am not wrong, there may be loss of packet but ping requests needs to be continuously sent.

CloudEnthusiast gravatar imageCloudEnthusiast ( 2016-09-14 08:36:14 -0500 )edit

You are right. There should be loss of packets but not ping interruption. I also faced the same problem. I assume you are using linux image for lunching vms. As far as I know, this is a kernel problem for linux.

fifi gravatar imagefifi ( 2016-09-14 13:55:28 -0500 )edit

Lets say a vm migrate from node A to node B and then you're gonna migrate it back from B to A. Don't do this immediately. After each migration, wait for a short while. Then check the console of the vm. In most cases, after a while you will see that the vm goes off

fifi gravatar imagefifi ( 2016-09-14 13:57:43 -0500 )edit

This is the reason why you cannot ping it during migration. In fact, wm is responsive a short while after migration and then it won't be responsive. In this case you need to soft reboot your instance and then make an attempt for new migration.

fifi gravatar imagefifi ( 2016-09-14 13:59:16 -0500 )edit

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Asked: 2016-09-13 06:08:43 -0500

Seen: 252 times

Last updated: Sep 13 '16