Server switchover is a feature that allows the user to switch over applications from a primary server to a predefined spare server when the primary server fails or is stopped for maintenance.
It can also perform Auto-Recovery, which automatically switches applications over to a spare server when a hardware failure is detected on the primary server.
There are the following four methods for switchover to spare servers.
However, each method has its own restrictions regarding supported server configurations (such as hardware environment and boot format). For details, refer to "9.2 Configuration".
When performing server switchover or failback using the backup and restore method, it is necessary to create a Windows PE in advance. For details, refer to the "Windows PE Creation Script Guide".
Method | Overview |
|---|---|
In a local boot environment, this method restores a system image backup to a spare server, which is then automatically started up. | |
In a SAN boot environment, this method sets the WWN of a spare server's HBA to the same value as that originally set on the primary server. This allows the spare server to connect to and boot from the same boot disk that was used by the primary server. | |
VIOM Server Profile Switchover method | This method is used in SAN boot environments where servers start from boot disks located in storage arrays. If the primary server fails, the WWN, MAC address, boot configuration, and network configuration that have been set in its server profile using virtual I/O (VIOM) are inherited by the spare server, which then automatically starts up from the same SAN disk. |
ISM Profile Switchover method | This method is used in SAN boot environments where servers start from boot disks located in storage arrays. If the primary server fails, the WWN, MAC address, boot configuration, and network configuration that have been set in its server profile using virtual I/O (ISM) are inherited by the spare server, which then automatically starts up from the same SAN disk. |
This method is used when the server is SPARC M10/M12 or SPARC Enterprise. When using this method, the boot disk connection destination is switched over to a spare server, in coordination with ETERNUS SF Storage Cruiser storage management functions. | |
Switchover | The operation that stops the primary server which is in operation and switches over to the spare server according to the specified server switchover method. |
Information
The VIOM server profile switchover method and the ISM profile switchover method are collectively referred to as the "Profile Switchover Method".
The profile switchover method and the HBA address rename method are collectively referred to as "I/O virtualization methods".
In a local boot environment, this method restores a system image backup to a spare server, which is then automatically started up.
This is selected under the following cases. For details on backup and restore, refer to "16.1 Overview" in the "User's Guide VE".
When a virtual WWN or boot configuration have not been set via the HBA address rename, VIOM, or ISM profile assigned to the primary server
When the [Local-boot with SAN data (Backup and restore method)] checkbox is selected during setting of the spare server
When HBA address rename, VIOM, or ISM has been used to set a profile for a server, the WWN and the profile also can be switched at server switchover.
After switchover, the operating system and its applications will resume on the spare server from the status they were in at the last system image backup.
Note that only the content of the first local disk (or boot disk) as seen by the BIOS of the managed server is subject to a backup or restore operation, including all partitions (Windows drives or Linux partitions) present on the boot disk.
However, since additional disks (disks used as data disks), are not subject to backup and restore, their content cannot be made automatically accessible to the spare server after server switchover.
When using more than one local disk, backup and restore of such additional data disks should be performed using external backup software.
However, when there are multiple sections on the first disk (Windows drives or Linux partitions), all sections become the targets of backup and restore.
In a SAN boot environment, this method sets the WWN of a spare server's HBA to the same value as that originally set on the primary server. This allows the spare server to connect to and boot from the same boot disk that was used by the primary server. This method is used when HBA address rename settings have been made on the primary server.
Because this method automatically starts the spare server from the primary server's boot disk, applications can be resumed without users being aware of the hardware replacement that occurred.
This method is used in SAN boot environments where servers start from boot disks located in storage arrays. If the primary server fails, the WWN, MAC address, boot configuration, and network configuration that have been set in its profile using virtual I/O (VIOM or ISM) are inherited by the spare server, which then automatically starts up from the same SAN disk. This method is used when a virtual WWN has been set via the VIOM or ISM profile assigned to the primary server.
Because this method automatically starts the spare server from the primary server's boot disk, applications can be resumed without users being aware of the hardware replacement that occurred.
When a primary server fails in a SAN boot environment, changing the following configuration using storage management software enables access and startup from the same boot disk. When HBA WWNs are fixed, reconfiguring storage devices enables continuation of operations.
Zoning settings for the Fibre Channel switches connected to servers
Host affinity settings for storage CAs
For PRIMERGY BX servers, the network configuration (VLAN IDs of adjacent LAN switch ports or port groups) of the primary server will be inherited by the spare server when using the backup and restore method, HBA address rename method, or the profile switchover method.
When using the profile exchange or the backup and restore method, if a MAC address, boot configuration, or network configuration were assigned to the server (in its profile), these settings will also be inherited by the spare server. Therefore, it is no longer necessary to reconfigure applications or network devices that depend on MAC address values.
Term | Description |
|---|---|
Switchover | The operation that stops the primary server which is in operation and switches over to the spare server according to the specified server switchover method. |
Failback | After server switchover is performed, this operation stops the operating spare server and switches back to the primary server. |
Takeover | The operation that appoints the active spare server as the new primary server instead of performing failback after switchover. |
Note
When using ServerView Deployment Manager on the admin LAN, the backup and restore method and HBA address rename are disabled. For details, refer to "B.2 Co-Existence with ServerView Deployment Manager".
Auto-Recovery occurs when a hardware failure is detected. However, it does not occur when the operating system has stopped as a result of a software error or when the operating system is automatically rebooted.
Refer to "9.4 Conditions Required for Auto-Recovery" for details.
Furthermore, since the Auto-Recovery is driven by a hardware failure, it prioritizes a fast recovery to a spare server instead of collecting an OS memory dump (which would be used to troubleshoot an OS failure).
Thus, even if a memory dump was set to be collected in the event of an OS failure, server recovery will take precedence and the memory dump will not be collected.
Server switchover can be realized using one of the following methods.
Backup and Restore Method
HBA address rename Method
Profile Switchover method
Storage Affinity Switchover Method
When configuring the HBA address rename function as the switchover method, first confirm that the HBA address rename settings have been configured properly before configuring the server switchover settings.
When server switchover is conducted using a Hyper-V VM host, prepare more than two physical NICs.
The network which VM hosts, such as the admin LAN for VM hosts, use to communicate with external servers should be dedicated only to physical servers, and not be configured for virtual networks.
In a network environment that has external virtual networks configured, disable all virtual networks for VM hosts. For details, refer to "9.2.1 Configuration Requirements" in the "Design Guide VE".
It is not possible to specify spare servers for individual VM guests. It is either possible to store VM guests on a SAN or NAS shared disk and assign a spare server to the VM host, or use the VM high-availability feature provided by the server virtualization software used.
For more details on the high-availability features available for each server virtualization software, refer to "9.2.2 Functional Differences between Products" in the "Design Guide VE".
Switchover using Resource Orchestrator, and the high-availability of server virtualization software can be used together.
When using a high-availability feature of server virtualization software, do not include spare servers of Resource Orchestrator in VM hosts as spare servers.
[VMware]
When using a high-availability feature (VMware HA) of server virtualization software, perform high-availability configuration again when performing server switchover or failback of Resource Orchestrator.
When primary and spare servers are placed in different chassis, and both servers are connected to LAN switch blades operating in IBP mode, server switchover only works if all of the following conditions are met.
LAN switch blades are PRIMERGY BX900/BX400
The same port group name is set for both LAN switch blades
When using Intel PROSet for LAN redundancy, the switchover destination server may inherit the same MAC address as that of the source server, as Intel PROSet keeps an internal definition of MAC addresses. When using Intel PROSet for LAN redundancy, the switchover destination server may inherit the same MAC address as that of the source server, as Intel PROSet keeps an internal definition of MAC addresses. To avoid communication issues caused by MAC address conflicts, please be sure to reconfigure MAC addresses on the destination server following a server switchover.
For servers other than blade servers, configuration is not possible when there are managed servers belonging to different subnets from the admin server.
Configuration is not possible when there are managed servers whose admin LAN NIC configurations are different from the primary server.
Server switchover can be performed, even if the NIC configurations used for HBA address rename setup service on the primary server and spare server are different. After server switchover is performed, the HBA address rename setup service may not operate depending on the network configuration. Therefore, the NIC configurations used for the HBA address rename setup service should be the same on both the primary server and the spare server.
For Linux managed servers, when the disks are recognized using the by-id name, server switchover cannot be performed using the backup and restore method.
When performing server switchover using the backup and restore method in a SAN data server environment that uses local boot, configure a target disk for image operations on both the primary server and the spare server.
If the switchover is performed without configuring the target disk for image operations, the data may be overwritten on an unintended disk.
For details, refer to "9.1.13 Changing Target Disks of Image Operations" in the "User's Guide VE".
In environments where there are servers running physical OSs and servers with VM hosts and VM guests, if they both use HBA address rename, VIOM or ISM, by combining the following settings it is possible for a physical OS and a VM guest to share a spare server.
For details, refer to "Figure 9.3 Sharing a Spare Server Between Physical OSs and VM Guests (High-availability Function of Server Virtualization Software)" in "9.2 Configuration".
Specify a VM host as the spare server used to recover VM guests within the high-availability feature (VMware HA) of the server virtualization software used.
Once the above settings have been made on a physical OS, a server failure will trigger the following recovery operations.
If the failed server was running a physical OS, Resource Orchestrator will shut down the VM host on the spare server and switch the failed physical OS over to the spare server. If the failed server was a VM host running VM guests, the high-availability feature provided with the server virtualization software will recover the VM guests on the spare VM host server. Since physical OSs and VM guests share a common spare server, the two types of recovery described above can perform together: once one type of recovery occurs on a spare server, another type of recovery can no longer be performed on that same spare server.
Information
Server switchover based on backup and restore takes approximately 3 minutes, plus the time required to restore the system image. Image restoration time depends on different factors such as disk space and network usage, but as an estimate, a disk of 73 GB will take 30 to 40 minutes (the transfer of the system images takes between 10 to 20 minutes, while system restarts and other configuration changes take another 20 minutes).
Server switchover based on HBA address rename takes approximately 5 minutes, plus the time required to start up the original operating system and services on the spare server. Server startup time is determined according to the time taken for starting the OS and the time taken for starting the services automatically when the OS is started. If a server OS was running on the spare server, the time required to shut down the spare server must also be included.
