This article covers frequently asked questions about reboot migrations and
live migrations as they pertain to the Rackspace Cloud.
Rackspace Technology migrates your servers for several reasons. Migrations optimize
data center resource usage, increase platform stability, and apply important
patches and upgrades to portions of the infrastructure. Rackspace Technology
periodically performs maintenance or decommissioning work on our cloud server
infrastructure, which might require the migration of cloud servers.
Typically, migrations use the live migration method, which generally does not
impact a server's uptime and responsiveness.
With live migrations, the virtual machine continues to run for the duration
of the migration. Operations can continue as expected, and no downtime should
occur during the course of the migration. Any data written or changed on the
server while the migration takes place floats over to the new hypervisor as well.
With reboot migrations, the server continues to run during migration. However, for
the migration to complete the cutover from the old to the new hypervisor, the system
reboots. During this reboot, differential and changed data on the server floats over
to the new hypervisor. The reboot process generally lasts from five to thirty
minutes, depending on the amount of data to transfer and the size of the server.
The time it takes for a migration to complete depends on a few factors. The
biggest determining factor is the underlying size of the VHD files that make
up the server's data footprint. Larger servers or servers that have been running
for a long time generally take longer to migrate than a server of a recent
build. For example, a 4GB General Purpose server that has been running for six
years is likely to have more VHD data than a newly created 8GB General Purpose
server. That being said, it is difficult to know exactly how long a migration takes.
In cases where Rackspace Technology cannot perform a live migration for any reason,
the system generates a ticket and sends it to your account to make you aware of
an upcoming reboot migration. This ticket contains information on the migration process,
why it is happening, and most importantly, it provides you with the date and time
of the reboot migration. At this point, you can choose to allow our automation
to perform the reboot migration as scheduled, or you can request in the ticket
that the migration happens at another date and time that works for you. After
your server migrates, your ticket information updates and closes to let you
know of its completion. You can also choose to migrate the server through your
Customer Portal as described in the following section.
At this time, initiating your own live migration is not possible, but you can
initiate a reboot migration on your server at any time. For more
information on how to migrate your server, see
Migrate a cloud server to a new physical host.
Because live migrations are non-impactful for the vast majority of
servers, you don't get notifications before every live migration.
Additionally, some live migrations are part of an unplanned, emergency
maintenance to move cloud servers away from unstable hypervisors. For
these reasons, you don't always receive notifications ahead of live migrations.
Live migrations can fail for several reasons. Primarily, they fail
because the cloud server operates outdated kernels that don't
cooperate with the hypervisor's effort to migrate the server. In
such cases, the cloud server can become unresponsive and ultimately
fail to migrate to the new hypervisor. In these cases, the system or technicians
generate tickets and schedule reboot migrations.
The more up-to-date your cloud server's operating system and kernel
is, the higher the success rate you see with live migrations. Also,
servers with very large data footprints can result in the live migrations
timing out while migrating to a new hypervisor, so avoiding older
larger flavors like 15GB or 30GB standard helps live migrations succeed.
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Updated 3 months ago