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OpenVZ Live Migration [message #31953]

Tue, 15 July 2008 21:51

shrin_krishnan
Messages: 2
Registered: July 2008

Junior Member

I was trying to understand better how Live Migration works in OpenVZ. Does it require shared storage, or does it move the checkpoint file over ?

If it does not use shared storage how does it maintain consistent fd's if say I am reading a file and doing a network file transfer.

Further, is there any residue on the originating host i.e are there connections maintained on the originating host ? How is the network connection migrated over. Xen and VMware require a shared switch where you send ARP's and change MAC registration. Is the same principle followed here

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Re: OpenVZ Live Migration [message #31966 is a reply to message #31953]

Wed, 16 July 2008 08:16

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

Senior Member

Checkpoint file it copied over the network. After migration an ARP announce is sent telling «this IP is now here». There is a short period of time when network packets are dropped and this is pretty normal — TCP packets will be resent, while UDP packets are supposed to be lost sometimes (application level handle it). Opened files and opened network connections are migrated.

If you need more details, see the OpenVZ kernel source code, the directory is kernel/cpt

Kir Kolyshkin

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

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Re: OpenVZ Live Migration [message #31969 is a reply to message #31966]

Wed, 16 July 2008 15:09

shrin_krishnan
Messages: 2
Registered: July 2008

Junior Member

What does it mean by opened files are migrated ? If shared storage is not a requirement, then either you copy the complete file over which could be pretty large. unless files are left on the original system and a connection is maintained.

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