On a Friday in 2021, Peter Krempa wrote:
Non-shared storage migration of guests which are disk I/O intensive and have fast local storage may actually never converge if the guest happens to dirty the disk faster than it can be copied.This patch introduces a new flag 'VIR_MIGRATE_NON_SHARED_SYNCHRONOUS_WRITES' which will instruct hypervisors to synchronize local I/O writes with the writes to remote storage used for migration so that the guest can't overwhelm the migration. This comes at a cost of decreased local I/O performance for guests which behave well on average. Signed-off-by: Peter Krempa <pkre...@redhat.com> --- docs/manpages/virsh.rst | 6 +++++- include/libvirt/libvirt-domain.h | 10 ++++++++++ src/libvirt-domain.c | 20 ++++++++++++++++++++ tools/virsh-domain.c | 13 +++++++++++++ 4 files changed, 48 insertions(+), 1 deletion(-) diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst index 7c50388216..1ce3e77c9f 100644 --- a/docs/manpages/virsh.rst +++ b/docs/manpages/virsh.rst @@ -3180,7 +3180,7 @@ migrate [--postcopy-bandwidth bandwidth] [--parallel [--parallel-connections connections]] [--bandwidth bandwidth] [--tls-destination hostname] - [--disks-uri URI] + [--disks-uri URI] [--copy-storage-synchronous-writes] Migrate domain to another host. Add *--live* for live migration; <--p2p> for peer-2-peer migration; *--direct* for direct migration; or *--tunnelled* @@ -3202,6 +3202,10 @@ images on source host to the images found at the same place on the destination host. By default only non-shared non-readonly images are transferred. Use *--migrate-disks* to explicitly specify a list of disk targets to transfer via the comma separated ``disk-list`` argument. +With *--copy-storage-synchronous-writes* flag used the disk data migration will +synchronous handle guest disk writes to both the original soure and the
synchronously
+destination to ensure that the disk migration coverges at the price of possibly
converges
+decreased burst performance. *--change-protection* enforces that no incompatible configuration changes will be made to the domain while the migration is underway; this flag is implicitly
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