Re: [libvirt] Live Migration with non-shared storage for kvm

16 Feb 2010

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"Daniel P. Berrange" <berrange@redhat.com> wrote on 26/01/2010 16:20:22:
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"Daniel P. Berrange" <berrange@redhat.com>
26/01/2010 16:20
Please respond to
"Daniel P. Berrange" <berrange@redhat.com>
To
Kenneth Nagin/Haifa/IBM@IBMIL
cc
Subject
Re: [libvirt] Live Migration with non-shared storage for kvm
On Tue, Jan 26, 2010 at 04:09:58PM +0200, Kenneth Nagin wrote:
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"Daniel P. Berrange" <berrange@redhat.com> wrote on 26/01/2010
12:14:47:
Since, this my first time submitting something to libvirt I wanted to
make
the initially submission simple, i.e. just adding the flags.
That sounds fine
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I suggest adding these flags to  virDomainMigrate.
That sounds reasonable.
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If I'm not mistaken qemuMonitorTextMigrate is the function that
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invokes the kvm monitor.
Thus, it would be necessary to pass the flags to
qemuMonitorTextMigrate..
But qemuMonitorTextMigrate does not have a flag input parameter.  I
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the least disruptive way to support the new flags is use the
existing
"background" parameter
to pass the flags.   Of course this would require some changes to
actually
think
the
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upstream functions that are invoked for migration.
That is an internal function, so adding extra parameters to it is no
problem at all - no need to reuse/abuse existing parameters.
Are you recommending adding another "flag" parameter or exploiting the
existing "background" parameter?
Probably define some flags for the internal API. eg in
src/qemu/qemu_monitor.h
add a small enum
enum {
   QEMU_MONITOR_MIGRATE_BACKGROUND = 1 << 0,
   QEMU_MONITOR_MIGRATE_STORAGE    = 1 << 1
   ...etc
 };
and then just replace the existing background parameter with a flags
parameter
Daniel
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Sorry about the delayed response.  I had some pressing work items and
family issues that took precedence.

In order to support kvm's live migration with non-shared storage I added
two
migration flags that user can invoke:

    VIR_MIGRATE_NON_SHARED_DISK   = (1 << 6), /* migration with non-shared
storage with full disk copy */
    VIR_MIGRATE_NON_SHARED_INC    = (1 << 7), /* migration with non-shared
storage with incremental copy */
                                              /* (same base image shared
between source and destination) */
Likewise I add complementary flags to virsh migrate: non_shared_disk and
non_shared_inc

As you suggested I also added internal flags to be passed in the
"background" parameter to the qemu monitor:
typedef enum {
  QEMU_MONITOR_MIGRATE_BACKGROUND         = 1 << 0,
  QEMU_MONITOR_MIGRATE_NON_SHARED_DISK  = 1 << 1, /* migration with
non-shared storage with full disk copy */
  QEMU_MONITOR_MIGRATE_NON_SHARED_INC   = 1 << 2, /* migration with
non-shared storage with incremental copy */
  QEMU_MONITOR_MIGRATION_FLAGS_LAST
};

I updated qemu_driver.c's doNativeMigrate and doTunnelMigrate to map the
external flags to the internal flags.
I updated qemu_monitor_text's qemuMonitorTextMigrate to map the internal
flags to the qemu monitor's command line flags.

I tested the doNativeMigrate usage of the two flags.  However, I could not
test the doTunnelMigrate usage because I wasn't sure how it works.  Also,
qemudDomainSave ends up calling qemuMonitorTextMigrate, but it didn't
support the external flags so I assumed that it was not relevant.

Here is the diff patch file from the current git:

(See attached file: migration_with_non_shared.patch)

- Kenneth Nagin

Kenneth Nagin

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