[New] Warm Migrations (#6711)

* [New] Warm Migrations

* copy edit

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* copy edit to live migration FAQ

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Co-authored-by: Matt Wildman <matt@wildman.online>

docs/products/compute/compute-instances/guides/compute-migrations/index.md

@@ -0,0 +1,101 @@
+---
+slug: compute-migrations
+title: "Compute Migrations on Akamai Cloud"
+description: 'This guide reviews the various types of compute migrations available on the Akamai Cloud platform.'
+keywords: ['migrate','migration','host']
+tags: ["linode platform","cloud manager"]
+authors: ["Linode"]
+published: 2023-11-14
+modified_by:
+  name: Linode
+
+---
+
+A migration occurs when a Compute Instance is moved from one physical host machine to another. This can happen within the same data center or across data centers. Migrations across data centers can be configured by customers in the Cloud Manager. All other types of migrations must be configured by a Linode or Akamai administrator.
+
+## Types of Migrations
+
+There are three types of migrations that can occur: **cold**, **live**, or **warm**.
+
+### Cold Migrations
+
+During a cold migration, your Compute Instance is automatically shut down (if it's not powered off already), moved to another physical host machine, and then returned to its previous state (booted or powered down) once it has fully migrated.
+
+- **Advantages:** Can occur within the same data center and across data centers, generally the most available type of migration option
+- **Disadvantages:** Requires the most downtime of all migration types
+
+### Live Migrations
+
+During a live migration, your Compute Instance remains up and running while it is moved from one host to another within the same data center.
+
+- **Advantages:** No downtime
+- **Disadvantages:** Not always an option depending on the scenario (i.e. host hardware compatibility, plan resizing, etc.)
+
+### Warm Migrations
+
+During a warm migration, your Compute Instance remains up and running while it is synced from one host to another within the same data center. Once synced, the instance is automatically powered down and is booted back up on the new host to complete the migration process.
+
+- **Advantages:** Significantly less downtime than a cold migration, alternative to live migrations if they are not available
+- **Disadvantages:** Requires a reboot to complete the process
+
+## When Migrations Occur
+
+Compute Instances can be migrated between hosts within the same data center and across data centers. Some of the reason for these migrations are detailed below. The type of migration that occurs (warm, live, or cold) depends on the situation as well as the host hardware on the origin and destination machine.
+
+**Within the same data center:**
+
+- Scheduled or emergency maintenance
+- By customer request via [Support ticket](/docs/products/platform/get-started/guides/support/) while troubleshooting performance issues
+- During the [resize process](/docs/products/compute/compute-instances/guides/resize/)
+
+Migrations within the same data center can be achieved via any migration type (cold, live, and warm).
+
+**Across data centers:**
+
+- Customer initiated for personal or business reasons (see our guide on [Initiating a Cross Data Center Migration](/docs/products/compute/compute-instances/guides/migrate-to-different-dc/))
+- By customer request via [Support ticket](/docs/products/platform/get-started/guides/support/)
+- When an old data center is retired. If this is the case, you will be notified ahead of any anticipated migrations or maintenance.
+
+Migrations across data centers can only be achieved using cold migrations.
+
+## Troubleshooting Migrations and FAQ
+
+### What if my cold migration fails?
+
+Should a cold migration fail for any reason, the Support team is notified and will configure a new cold migration.
+
+### Why would a live migration not be available?
+
+In order for a live migration to occur, a host compatible with the host your instance currently resides on must be available. Not all host hardware is alike or available to accept a live migration, so live migrations are not always a viable option.
+
+### What could cause a warm migration to fail?
+
+-   Your instance is not configured to respect ACPI shutdowns:
+    - This applies to warm migrations initiated by customers, including warm migrations taking place during the warm resize process.
+    - This also applies if you are running a custom distribution (i.e. Windows) or unsupported disk image that is not configured for ACPI shutdowns.
+-   If a Linode or Akamai administrator cancels the warm migration.
+-   If the sources Linode stops responding, is shut down prior to the cross-host sync, or if the process is disturbed in any way.
+
+### What should I do if my warm migration fails?
+
+-   If your warm migration fails to complete after an early initiation is triggered via the Cloud Manager, the Support team is notified. There are two options that are used at the discretion of the Support team.
+    - A new warm migration can be configured to be performed at a scheduled time.
+    - A cold migration can be configured. You can then initiate the cold migration via the Cloud Manager or allow it to proceed as otherwise scheduled.
+
+### What should I do if my warm resize fails?
+
+- If a warm resize fails, you can either proceed with a cold resize (recommended) or troubleshoot your instance's configuration to respect ACPI shutdowns.
+
+### What if my cross data center migration fails?
+
+- Should a cross data center migration fail, you may reattempt the migration. If it fails again, open a [Support ticket](/docs/products/platform/get-started/guides/support/) for further assistance.
+
+## Next Steps
+
+If you want to learn more about migrations or need additional troubleshooting tips, see the following resources for additional information:
+
+- [Guides - Change Plans (Resize)](/docs/products/compute/compute-instances/guides/resize/)
+- [Guides - Reboot Survival Guide](/docs/guides/reboot-survival-guide/)
+- [Linode Community - How should I handle a Scheduled Migration for my Linode?](https://www.linode.com/community/questions/23075/how-should-i-handle-a-scheduled-migration-for-my-linode)
+- [Linode Community - My Linode is unreachable after maintenance](https://www.linode.com/community/questions/323/my-linode-is-unreachable-after-maintenance)
+- [Linode Blog - Live Migrations at Linode](https://www.linode.com/blog/linode/live-migrations-at-linode/)

docs/products/compute/compute-instances/guides/resize/index.md

@@ -2,7 +2,7 @@
 description: "A walkthrough on upgrading or downgrading a Compute Instance's plan, including switching to a different plan type."
 keywords: ["upgrading", "resizing", "disk space"]
 tags: ["linode platform","cloud manager"]
-modified: 2023-08-22
+modified: 2023-10-31
 modified_by:
   name: Linode
 published: 2017-02-14
@@ -19,21 +19,29 @@ Changing a Compute Instances plan (and plan type) is made easy through the Cloud
 
 - You can upgrade your Compute Instance to a larger plan, downgrade to a smaller plan, or even change to a different plan type (such as switching from a Shared CPU plan to a Dedicated CPU plan).
 
-- While resizing a Compute Instance, it is powered off and migrated to a different physical host within the same data center. This new host may have slightly different hardware, though performance is consistent across our entire fleet.
+- While resizing a Compute Instance, it is migrated to a different physical host within the same data center. This new host may have slightly different hardware, though performance is consistent across our entire fleet.
 
 -  The disks are transferred to the new hardware at a typical rate of ~150 MB/sec. While you can use this rate to approximate any downtime, the actual transfer speeds may vary and downtime may be shorter or longer than expected.
 
-- The Compute Instance remains powered off during the entire resize process. After the resize completes, the instance returns to its previous power state.
+- You can choose from two resize types: a **warm resize** or a **cold resize**. Which type of resize you choose will determine the amount of downtime your instance will experience when migrating from one host to another. See [Warm Resize vs. Cold Resize](#warm-resize-vs-cold-resize) to determine which resize type is right for you.
 
-- All of your existing data and configuration settings are preserved during the resize and your IP addresses remain the same.
+- All of your existing data and configuration settings are preserved during the resize, and your IP addresses remain the same.
+
+## Warm Resize vs. Cold Resize
+
+There are two resize options to choose from when configuring your resize: **warm** and **cold**. The terms “warm” and “cold” refer to the [type of migration](/docs/products/compute/compute-instances/guides/compute-migrations/) that occurs during the resize process. Your instance must be powered on in order to attempt a warm migration. If your instance is powered off, you may proceed with a cold migration.
+
+- **Warm resize:** A warm resize will make sure your Compute Instance remains up while migrating to a new host prior to being rebooted. During this process, your instance is synced across hosts while running, automatically powers off, goes through the resize job, and boots back up to complete the resize. If your instance fails to automatically power off, you will be notified of the failed job attempt. Should the warm resize fail, we recommend reattempting the resize process using the cold resize option. There is less downtime during a warm resize than a cold resize.
+
+- **Cold resize:** A cold resize will shut down your Compute Instance, migrate it to a new host, and restore it to its state prior to the resize process (either booted or powered off). There is more downtime during a cold resize than a warm resize.
 
 ## Resizing a Compute Instance
 
 1.  Log in to the [Cloud Manager](https://cloud.linode.com) and select the **Linodes** link within the left sidebar.
 
-1.  Within the list of Compute Instance, locate the instance you'd like to resize, click the corresponding **more options ellipsis** dropdown menu, and select **Resize**. This displays the **Resize Linode** panel.
+1.  Within the list of Compute Instances, locate the instance you'd like to resize, click the corresponding **more options ellipsis** dropdown menu, and select **Resize**. This displays the **Resize Linode** panel.
 
-    ![The Resize Linode panel in the Cloud Manager](resize-linode-plan.png)
+    ![The Resize Linode panel in the Cloud Manager](resize-linode-plan.jpg)
 
 1.  Select the desired plan.
 
@@ -43,6 +51,8 @@ Changing a Compute Instances plan (and plan type) is made easy through the Cloud
 
     -  **To select a different plan type**, review [Switching to a Different Plan Type](#switching-to-a-different-plan-type).
 
+1. Under **Choose Your Resize Type**, select **warm resize** or **cold resize** to determine how you would like your instance to resize. See [Warm Resize vs. Cold Resize](#warm-resize-vs-cold-resize) to help decide which option best suits your use case.
+
 1.  Check **Auto Resize Disk** if you'd like to automatically resize your Compute Instance's primary disk. This can only be selected if the following conditions are met:
 
     - The new plan provides more storage space than the current plan.
@@ -52,7 +62,7 @@ Changing a Compute Instances plan (and plan type) is made easy through the Cloud
 
 1.  Enter the Compute Instance's label in the **Confirm** field and select the **Resize Linode** button to initiate the resize.
 
-1.  If the instance is powered on, it will now be powered off for the duration of the resize. After the resize completes, the instance returns to it's original power state.
+1.  If performing a warm resize, your instance will be powered on to complete the resize process. If performing a cold resize, your instance will return to its original power state (powered on or off).
 
 You are now able to utilize the resources of your new plan.
 
@@ -105,5 +115,13 @@ See below for the different Compute Instance plan types available:
 - **GPU:** The only plan type that is equipped with high performance NVIDIA GPU cards. GPU plans are capable of processing large amounts of data in parallel, performing complex calculations much more efficiently. See [GPU Compute Instances](https://www.linode.com/products/gpu/).
 
 {{< note >}}
-Not all plan types are available in all regions. See [How to Choose a Data Center](/docs/products/platform/get-started/guides/choose-a-data-center/#product-availability) for plan and product availability.
-{{< /note >}}
+Pricing and plan options may vary by region. See our [Pricing](https://www.linode.com/pricing/) page for more information on pricing options and [How to Choose a Data Center](/docs/products/platform/get-started/guides/choose-a-data-center/#product-availability) for plan and product availability.
+{{< /note >}}
+
+## Troubleshooting
+
+- **If a warm resize fails:** Should the warm resize process fail for any reason, you will receive a notification in Cloud Manager, as well as an email notification regarding the failed job. There are several reasons a warm resize may fail, including the inability to successfully reboot due to internal configuration settings. If this is the case, we recommend proceeding with a cold resize.
+
+- **If a cold resize fails:** Should the cold resize process fail to complete, we recommend reattempting the resize. If it continues to fail, reach out to our [Support](/docs/products/platform/get-started/guides/support/) department for assistance.
+
+For additional information on troubleshooting resizes or migrations, please see our [Compute Migrations](/docs/products/compute/compute-instances/guides/compute-migrations/) guide.