Migration guide for ECS using local disks

Technical additional documentation

Context

Usually, ECS rely on Elastic Volume Service (EVS) to provide System disk & Data disk

There is some exceptions where  some local disk are used for some specific use case.

The subject of that article is to handle that situation from a migration point of view.

List of ECS using local disks

 
Service Type

Name

Local disk configuration

For
ECS Disk Intensive

 d2

 d3

 d6

From 2 to 24*1.8TB

From 2 to 28*1.8TB

From 2 to 36*7.4TB

Data disk

Data disk

Data disk
ECS

Ultra-high I/O

  i3 From 1 to 12*1,8TB Data disk

 

Limitations

In such case,

  • ECSs cannot be migrated when the physical server becomes faulty,
  • ECSs do not support specifications modification.
  • ECSs do not support local disk snapshots or backups.
  • ECSs can use local disks, and can also have EVS disks attached to provide a larger storage size. Note the following when using the two types of storage media:
    • Only an EVS disk, not a local disk, can be used as the system disk of ECS.
    • Both EVS disks and local disks can be used as data disks of ECS.

How to migrate ECS (d & i series) with local disks

There is many way to initiate ECS to ECS migration in such situation. In any case, because local disk of the ECS is not EVS based

  • User can’t rely on a one step action through a full ECS backup/restore with CBR Server backup, nor with some ECS resizing feature.
  • User should adapt the proposed process below, integrating some operation inside the ECS, ate the Operating Syetem level, depending on it (mainly Windows versus Linux)

We can consider some Flexible Engine services to help for the migration. Mainly 2 services are scoped for that

  • Server Migration Service SMS, design to migrate any workload from on VM (on premise or in the cloud) to an ECS can be used
  • Cloud Backup & Recovery CBR, the Flexible Engine backup service can be useful, for any EVS of the ECS (mainly the system disk)

Migrating ECS with SMS

Server Migration Service (SMS) helps user migrate applications and data from x86 physical or virtual servers on premises or in another cloud to Elastic Cloud Servers (ECSs) on Flexible Engine. SO the source Virtual Machine can be an ECS as well.

The SMS concept is to install in the source machine an SMS Agent to replicate the full disk (system & data disks) to a target server

As illustrated on the diagram, the source server is an ECS & some EVS disks (for system & Data), so the proposed process will :

  • replicate the source EVS disk for system to EVS system disk
  • replicate all the source EVS disks for Data if any exist,  to EVS data disks
  • replicate all the source local disks for Data if any exist,  to EVS data disk

Note that the SMS migration will not provide an iso situation for local disk, since SMS is not able to replicate source local disk to target local disk

Then, after using SMS to replicate the ECS, Admin user shoud add a step to replicate locally to the target ECS the EVS data disk to loca disk, as it was configured in the source ECS.

 

So let consider the following situation : as user, I want to migrate my ecs-i3-source ECS from eu-west-0c to eu-west-0a

So the proposed migration path to do that is as follow

Step 1

Install SMS agent onto the current ECS

  • This step consist on :
    • Downloading the ICAgent depending on the source Operating system (Widnwos versus Linux) from Flexible Engine repository
    • Install the ICAgent locally inside the ECS, running the installer
  • Refer to Online Help for detailed information : https://docs.prod-cloud-ocb.orange-business.com/usermanual/sms/sms3_02_0004.html
  • Note you will need an AK/SK of a authorize Admin to start the ICagent and build/encrypt the secure connection between SOurce & Target, refer to to create such AK/SK https://docs.prod-cloud-ocb.orange-business.com/usermanual/iam/iam_01_0618.html

Connect Flexible Engine to check the status of ICAgent. After started ICAgent, the SMS Console should show the ECS as a possible source to replicate
Step 2

Create the migration task, targeting an equivalent ECS configuration to create during the process (creation by SMS directly is possible)

  1. Select the source ECS to replicate and configure priority option for the task (Advanced settings)

     

  2. Configure the task by selecting

    • “Private line” Network type
    • Target ECS to “Create during migration”
    • No template
    • Specify your VPC & NIC to host the target ECS
    • “Auto create” for Security Group
    • Then click “Advanced Settings”

  3. Fill aditionnal Advanced settings

    • Select the AZ1 to locate the target ECS in eu-west-0a, as requested
    • Select the same flavor for target & source
    • Select the same Disk Type & Size for system disk
    • Please notice SMS detect the source local disk for Data and propose an EVS Data disk of the size of the source local disk


  4. The ECS target configuration will be like that


    Note that /dev/sdb stand for the Data disk of the i3, and has been automatically configured as EVS Data disk!
Step 3

Run the task and wait until it’s fully completed

Nota bene : to limit the downtime on the source server, you can use the “incremental synchronisation” of SMS
To replicate the source local disk data to the target ECS, remember SMS replicate local disk to attached EVS disk. For that reason, the Admin System of the ECS should Connect the ECS target
Step 4

To Arrange the network setting (Security group setting) in order for the target ECS (newly created) to be accessible
Step 5

To configure the local disk according to the Operating System and the size of the partition. Check the Online Help for any information https://docs.prod-cloud-ocb.orange-business.com/usermanual/evs/evs_01_0038.html

Partitioning Operation Guide

Note the device name of a local disk depend on the flavor

  • ECS i Serie : attached to an ultra-high I/O ECS is /dev/nvme0n1 or /dev/nvme0n2
  • ECS d Serie : you are advised to use World Wide Names (WWNs), but not drive letters, in applications to perform operations on local disks to prevent drive letter drift (low probability) on Linux. Take local disk attachment as an example:

    If the local disk WWN is wwn-0x50014ee2b14249f6, run the mount /dev/disk/by-id/wwn-0x50014ee2b14249f6 command.

    How can I view the local disk WWN?

    1. Log in to the ECS.
    2. Run the following command:

      ll /dev/disk/by-id

For a disk smaller than 2 TiB, see the following sections : 

  • Initializing a Windows Data Disk (Windows Server 2008)
  • Initializing a Windows Data Disk (Windows Server 2019)
  • Initializing a Linux Data Disk (fdisk)
  • Initializing a Linux Data Disk (parted)

For a disk larger than 2 TiB, see the following sections :

  • Initializing a Windows Data Disk Larger Than 2 TiB (Windows Server 2008)
  • Initializing a Windows Data Disk Larger Than 2 TiB (Windows Server 2012)
  • Initializing a Linux Data Disk Larger Than 2 TiB (parted)
Step 6

To Copy data from the EVS Data volume of the target ECS to the local disk newly configured

Warning : be sure any application accessing the Data disk is stoped before starting the copy 

For Windows Operating Server, there is many way to replicate a full volume. One of the more robust tools usefull in any Windows version is robocopy. Check https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/robocopy for help

For Linux Operating Server, you can use rsync or dd command to replicate any Data partition. Check https://manpages.org/rsync man pages for rsync

Nota bene : to limit the downtime on the source server, you can run an “incremental synchronisation” when your selected Sys Admin tools can do (rsync & robocopy can)
Step 7

Then stop the source server
Step 8

Review the network configuration of the new ECS (target server) and of all VPC network settings
Step 9

If any rollback is required, you just need to stop the Target server & restart the source one