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migration? [message #29372]

Fri, 11 April 2008 13:21

shuaib85
Messages: 59
Registered: September 2007

Member

Dear all

is there any other article about migration and checkpoint beside this in the wiki
http://wiki.openvz.org/Checkpointing_and_live_migration

I have questions
When we migrate, What happens to the data that is cached in the memory?

How long the container will be down in case of migration online (I tried it is about 50 seconds for centos template)

Thanks

WebVZ: OpenVZ Web Management Tool
http://webvz.sourceforge.net

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Re: migration? [message #29384 is a reply to message #29372]

Fri, 11 April 2008 16:12

kir
Messages: 1645
Registered: August 2005
Location: Moscow, Russia

Senior Member

shuaib85 wrote on Fri, 11 April 2008 17:21

Dear all

is there any other article about migration and checkpoint beside this in the wiki
http://wiki.openvz.org/Checkpointing_and_live_migration

There's also http://wiki.openvz.org/Checkpointing_internals

Quote:

I have questions
When we migrate, What happens to the data that is cached in the memory?

Do you mean filesystem cache maintained by the Linux kernel? Or do you mean some user application's data?

Quote:

How long the container will be down in case of migration online (I tried it is about 50 seconds for centos template)
Thanks

I've seen numbers from 3 to about 10 seconds (vzmigrate -v should print timing stats). There are a few things that affect "offline" time. One particular thing is since ssh/scp is used a few times during migration, you have to set up destination system in a way that each ssh connect doesn't lead to a long IP-to-hostname DNS lookup. One way of doing that is putting your source system IP on the destination node. There are a lot of other stuff that can/should be checked.... We need to see your numbers if you need some help with that.

Kir Kolyshkin

http://static.openvz.org/userbars/openvz-developer.png

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Re: migration? [message #29450 is a reply to message #29384]

Sun, 13 April 2008 05:08

shuaib85
Messages: 59
Registered: September 2007

Member

Quote:

Do you mean filesystem cache maintained by the Linux kernel? Or do you mean some user application's data?

Yes I mean user application's data for example web server.

Quote:

How long the container will be down in case of migration online (I tried it is about 50 seconds for centos template)
Thanks

I've seen numbers from 3 to about 10 seconds (vzmigrate -v should print timing stats). There are a few things that affect "offline" time. One particular thing is since ssh/scp is used a few times during migration, you have to set up destination system in a way that each ssh connect doesn't lead to a long IP-to-hostname DNS lookup. One way of doing that is putting your source system IP on the destination node. There are a lot of other stuff that can/should be checked.... We need to see your numbers if you need some help with that.

I have migrated one container and this is the time output
Restoring completed succesfully
Resuming VE
Resuming...
Times:
Suspend + Dump: 0.334938
Copy dump file: 16.682
Second rsync: 24.7136
2nd level quota: 12.5953
Undump + Resume: 11.9137
Total time: 66.2395
Cleanup

As you can see the total time is 66 seconds!!

I used ping to check the availability of the container. About 50 ICMP were either missed or telling Time to live exceeded, others tell redirect to host

WebVZ: OpenVZ Web Management Tool
http://webvz.sourceforge.net

[Updated on: Sun, 13 April 2008 05:10]

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