With more and more companies moving to Cloud Computing, provisioning of proper DR (Disaster Recovery) and DA (Disasater Avoidance) had became a must component of any infrastructure plan. As we move from physical datacenters to virtual clouds, lets have a look at the components and resources required to achieve the desired infrastructure availablity.
One of the main concepts of cloud computing is
providing almost unlimited resources for a given service, automatically
and dynamically, in a fully-virtual environment. To provide those
resources, the complete cloud computing architecture must be built with
efficient tools and support business continuity throughout its compute,
network, and storage resources. Four
technical services are essential to supporting the high level of
flexibility, resource availability, and transparent resource
connectivity required for cloud computing:
•
The Layer 3 network offers the traditional routed interconnection
between remote sites and provides end-user access to cloud services.
•
The extended LAN between two or more sites offers transparent transport
and supports application and operating system mobility.
• Extended SAN services support data access and accurate data replication.
• IP Localization improves northbound and southbound traffic as well as server-to-server workflows.
Cisco Data Center Interconnect (DCI) provides us with a detailed reference solutions support the extension of
network, storage and compute resources for multiple data centers in
multiple locations. When we talk about building a cloud, Most important component is Disaster Recovery and we must have look at the types of DR options available today -
Cold Standby - This is the most basic type of DR options. Replica of all the applications, network infra, and data is kept at the backup location but all the applications need to manually started and data redirection has to done manually on the datacenter end. Mean Time to Switch is highest in this type of DR. The time to recover, also known as Recovery Time
Objective (RTO), for this scenario can require up to several weeks. In
addition, the Recovery Point Objective (RPO), which is the maximum data
lost during the recovery process, is quite high. It is accepted that
several hours of data might be lost in this type of DR. Below is the diagram for Cold Standby -
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| Cold Standby DR Option - Image by Cisco |
Warm Standby - This is another option where appliactions and resources at the DR site are kept ready to start and can be used just by redirecting the traffic to the DR location. We can expect better RTP & RPO in this case but still it is not as transparent as Hot Standby
Hot Standby - Okie... The hottest one.. In hot standby mode, the backup data center has
some applications running actively and some traffic processing the
service tasks. Data replication from the primary data center and the
remote data center are done in a real time. Usually the RTO is measured
in minutes and the RPO approaches zero, which means that the data
mirrored in the backup site is exactly the same as that in the original
site. With this all applications and services can be started without any delay
Now when we say Data Replication, It is done via Layer 3 interconnections between data centers through a highly-available routed WAN but for replicating the data Cisco depends on the various other OEMs. We can depend on the following products for our solution -
Veritas Volume Replicator
host-based mirroring solution, the host is responsible for duplicating
data to the remote site. In the EMC Symmetrix Remote Data Facility (SRDF) and Hitachi (HDS) TrueCopy disk-based mirroring solutions
With this we are done with the types of DR, Stay tuned for Disaster Avoidance for Cloud Computing.
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