Re: [Xen-devel] live migration with DRBD devices

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I want to do live migration of domains using DRBD block devices for
> synchronisation between the two Xen hosts with Xen 2.0.7.
>
> I've written a script ( block-drbd ) which binds / unbinds DRBD devices for
> specific domains (with DRBD, only one host can write on a drbd device at
> the same time). This script sets the current host as master (bind) or
> secondary (unbind) in a DRBD "Netword-RAID"

Yep - btw this is fixed with DRBD 8 (still in development), which supports 
multiple writers.

How are you handling the sequencing here, though?  Move the device to the new 
host at *unbind* time from the origin?  I'm thinking that the DRBD script 
will get run at the destination whilst the origin domain is still running and 
using its disk...

> xc_linux_save start 8
> [1130244324.174077] Saving memory pages: iter 1   0%
> Saving memory pages: iter 1   0%Error when writing to state file (5)
> Error when writing to state file (5)
> 2790 [WRN] XFRD> Transfer errors:
> 2790 [WRN] XFRD> state=XFR_STATE    err=1
> 2790 [INF] XFRD> Xfr service err=1
>
>
> Does anybody have an idea? I'd appreciate.

Weird...  Does this work without your script?  Does migration work with a 
simpler domain?  If you boot a domain from an initrd (removing disk 
dependencies), will that migrate correctly?

If it's something weird in the migration-related code, somebody else might 
have some further ideas as to what caused this...

Cheers,
Mark

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