GSLB (global server load balancing)

[Update: May 15, 2019]

This page explains the detailed specifications and operation instructions of the En-hanced Load Balancer appliance .

1. Overview

GSLB is an appliance for actualizing a load balancing environment among the regions of SA-KURA Cloud as well as some of our company’s other services, including SAKURA VPS and SAKURA Dedicated Server.

As this is provided as an appliance that can be created and configured from the Cloud Control Panel like VPC router and Load balancer , it is possi-ble to disperse loads and develop a redundant system quickly and easily.

See also

For information on the differences between the enhanced load balancer, GSLB , and Load balancer , please refer to the FAQ section What are the differences between the three types of load balancer appliances? .


For our fee schedule, please refer to Service site .

2. Specifications

Appliances currently provided are as follows.

Compatible protocol for network monitoring IPv4 (not compatible with IPv6)
Number of real servers that can be registered per GSLB Up to 6
TTL of DNS response 10 sec. (fixed)
Real server weight setting For each real server a weight value can be set as an integer value between 1 and 10,000.
Response when all real servers fail 1. Where there is an activated real server and set sorry server, if any enabled real serv-er is up, the active IP address will be returned
If all enabled real servers are down, the sorry server IP address will be returned.
2. Where there are no activated real servers and a sorry server is set, the sorry server IP address will be returned
Types of health checks that can be set Select a monitoring method from http, https, ping, and tcp.
Configurable health check interval 10 to 60 sec. (*Can be set in units of 1 sec)
Configurable health check options HTTP/HTTPS: Host header/path/status code
TCP: port number

*This service uses the DNS CNAME and cannot be used in conjunction with FQDN that is unable to configure CNAME, such as “” *Also support Punycode settings starting with xn–.

The health check is conducted from the IP address range listed below. At a registered real server, please specify settings to ensure correct response to health check types specified from each of the IP address ranges listed below.

3. Usage procedures

DNS is created and set through the following procedures.

Creation of an NFS appliance

Select DNS from the Global category of the menu on the left side of the control panel. Created zones are listed on the main screen. You can create a new zone by clicking the Add button.

A screen for creating a new zone will be displayed. Select and enter the required fields then click Create.

The explanation of each item is as follows.

Monitoring method (*) Specify a method for monitoring the servers for load balancing designated with IP ad-dresses and port numbers containing http, https, ping, and tcp.  
If http or https is specified, additional setting items will be displayed allowing configura-tion of a host header, a path to be monitored, and a response code for normal conditions.
If tcp is specified, additional setting items for port numbers to be monitored will be dis-played.
Check interval (sec.) (*) Set the interval for live monitoring of real servers. The set value is an integer value between 10 and 60.
Weighting response (*) For each IP address set for a real server, select whether or not to do the weighting setting that can adjust response probability.
Sorry server Set a backup destination when all balancing destinations are down.
Name/explanation/tag/icon As with servers, disks, and other appliances, easy-to-understand name settings, tags, and classification by the: ref: icon <icon> function are possible.

” indicates a required field.
*Monitoring Method and Check Interval, specified at the time of creation, can be changed by clicking the Change Monitoring Method button on the GSLB details screen. (Update is un-necessary).
*Setting a sorry server is not mandatory.
*A sorry server created by the customer is required (the server fee will be charged separately).

When creation is complete, it will be added to the List screen of created GSLBs. The FQDN can be confirmed at the time of creation.

*After selecting a target GSLB from the GSLB List screen, click Details to open the GSLB Details screen. From this screen, a GSLB can be deleted on by clicking Delete.

Registering a real server

Specify the real servers to be the GSLB’s load balancing destination(s). After selecting a target GSLB from the GSLB List screen, click Details to open the GSLB Details screen. Se-lect the Real Server tab, to display the list of real servers. To add a real server, click Add.

The Add Monitoring screen will appear. Enter the required fields.

The explanation of each item is as follows.

IP address Specify the IP addresses of the real server.
Enabled/disabled Specify whether a real server is to be load balanced.
Load balancing will apply immediately upon being added, providing Enable is specified at the time of configuration.
Weight Specify the response probability of each real server IP address by using integer values from 1 to 10,000.

Example: If three real servers are registered with weights of 1, 3, and 5, respectively, each real server’s IP address will respond with a ratio of 1:3:5.

*The Weight Value configuration items are indicated only when the Weighting Re-sponse function is enabled.

A newly configured real server will be added to the list of real servers. When settings are complete, click Update , to apply settings to the GSLB appliance.

*Settings of a real server can be changed by clicking the Pencil icon pf_pencil located at the right of the List screen. (After changing the settings, click the Update button). * A real server can be deleted by clicking the Deletion icon pf_pencil located at the right of the List screen. (After changing the settings, click the Update button.)

DNS registration of FQDN

When GSLB preparation is complete, register the host name to be load balanced as the CNAME of the FQDN.

*Example of a zone file where “” is set as the load balancing host name. IN CNAME

*For CNAME, specify FQDN displayed on the GSLB Details screen.

4.Configuration example

The following is an example of configuration using GSLB.

Redundant/load balancing configuration with servers installed in Tokyo/Ishikari regions

Configuration for distributing access from the Internet to servers installed in Tokyo and Ishikari regions via GSLB.

If the server at each site is stable, load balancing will be conducted through the DNS round robin. Dynamically updated content will be synchronized via a bridge that is connected to the local network on the backend-side.

If any server goes down, the IP address of the downed server won’t respond. Access from the Internet side will continue.

Configuration combining Load Balancer

By setting the load balancing target of GSLB to the VIP of the Load Balancer appli-ance, you can utilize it’s high-performance load balancing tools such as the configuration of mul-tiple real servers and granular monitoring.

5. Other

Operation Fundamentals

  • If all configured real servers experience a monitoring error, all IP addresses will respond. If a sorry server has been set, its IP address will respond.
  • Without session handling, there is no upper limit to the number of simultaneous connec-tions, number of sessions, etc.

Redundancy Function

  • The time required to complete exclusion from a load balancing destination after detec-tion of a monitoring error and/or incorporation into a load balancing destination after monitoring error recovery is at least 30 sec.
  • Due to DNS-based load balancing, reflection of load balancing destinations may be fur-ther delayed according to the DNS cache status on the client side, etc.
  • If the site requires rapid failover, we recommend configuration that incorporates the Load Balancer appliance.
  • When using GSLB for redundancy purposes, we do not recommend the use of weight setting from the viewpoint of high-speed failover.

Regarding the load balancing function

  • Load balancing functions as an equivalent to DNS round robin.
  • If granular balancing is required for each connection, we recommend a configuration that incorporates the Load Balancer appliance.

FAQ and answers

For questions or concerns regarding GSLB, please refer to our FAQ page .