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 <pkrempa@xxxxxxxxxx>
---
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
Jano
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