Difference between revisions of "TodoPreMigrationChecks"

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(Pre-migration compatibility checks)
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It's not possible, or at least not wise, to allow migration
 
It's not possible, or at least not wise, to allow migration
from any host to any other host.  In particular CPU capabilities
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from any host to any other host.  There are a whole host of things that need to be set up precisely the same on both the source and destination side for migration to have any chance of workingLibvirt should have some sort of pre-migration call that, given a destination host, will tell you whether a migration from here to there is likely to succeed.
differ unless the CPUs are absolutely identical(Even minor
 
stepping differences can, in theory, cause problems).
 
  
In addition, the logic of checking compatibility is very complicated.
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For such a call to be widely useful, the libvirt API would have to allow a caller to specify which of the available checks they are interested in, and then have some sort of return value that indicated if there are show-stopper problems, or just problems that may cause things to be sub-optimal on the remote side.  The caller can then decide what action it wants to take.
  
Libvirt should offer an API to allow this checking, which would
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The corollary to this "will migrate succeed" call is a call which, given two hosts A and B, figure out the lowest common denominator a guest needs to be run at so that migration in the future will likely be successful.
return a list of possible problems if migration were to take place.
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There are a lot of things that can/should be checked on both the source and destination side; the list includes:

Revision as of 16:03, 1 September 2008

Pre-migration compatibility checks

It's not possible, or at least not wise, to allow migration from any host to any other host. There are a whole host of things that need to be set up precisely the same on both the source and destination side for migration to have any chance of working. Libvirt should have some sort of pre-migration call that, given a destination host, will tell you whether a migration from here to there is likely to succeed.

For such a call to be widely useful, the libvirt API would have to allow a caller to specify which of the available checks they are interested in, and then have some sort of return value that indicated if there are show-stopper problems, or just problems that may cause things to be sub-optimal on the remote side. The caller can then decide what action it wants to take.

The corollary to this "will migrate succeed" call is a call which, given two hosts A and B, figure out the lowest common denominator a guest needs to be run at so that migration in the future will likely be successful.

There are a lot of things that can/should be checked on both the source and destination side; the list includes: