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3.1 Addressing Objects

Applications connect to storage nodes over HTTP either by IP address or by DNS hostname. You are strongly encouraged to use DNS hostnames when addressing an HCP system.


HCP periodically updates DNS records to reflect which storage nodes are up, running, and actively accepting traffic. Here’s an example query for the IP address of the hostname www.hcp01.hitachi.com.

$ dig www.hcp01.hitachi.com

; <<>> DiG 9.6.1-P2 <<>> www.hcp01.hitachi.com

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20452

;; flags: qr rd ra; QUERY: 1, ANSWER: 8, AUTHORITY: 0, ADDITIONAL: 0


;; QUESTION SECTION:

;www.hcp01.hitachi.com. IN

A

;; ANSWER SECTION:

www.hcp01.hitachi.com. 15


IN


A


172.20.2.74

www.hcp01.hitachi.com. 15

IN

A

172.20.2.75

www.hcp01.hitachi.com. 15

IN

A

172.20.2.76

www.hcp01.hitachi.com. 15

IN

A

172.20.2.77

www.hcp01.hitachi.com. 15

IN

A

172.20.2.78

www.hcp01.hitachi.com. 15

IN

A

172.20.2.79

www.hcp01.hitachi.com. 15

IN

A

172.20.2.80

www.hcp01.hitachi.com. 15

IN

A

172.20.2.81


As you can see, the HCP system is accessible from eight storage nodes. If a storage node becomes unavailable, HCP will remove its IP address from the DNS record for www.hcp01.hitachi.com.


You can leverage this behavior to


load balance traffic amongst storage nodes,


provide fault tolerance in the event of storage node failures, and


build disaster-recovery functionality into mission-critical applications


 

3.1.1 Load Balancing3.1.2 Fault Tolerance3.1.3 Disaster Recovery