Ashwinee Kumar

Nov 2015

Data CenterEcommerce Series – Part 4

Data Center

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Data Center

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• Two or more data centers helps to ensure availability by providing resiliency against • natural disasters• human errors • upstream outages• software problems cut.

Challenges with multi Data Center model

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1. Concurrent user login leading to data corruption – two family member logging in

2. Logic for routing traffic to either one of the multiple DC’sa) DNS server can have multiple records one for each DCb) Intelligent system called GSLBc) CDN that offers GSLB

Data Center Approach 1 – Active/Passive

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Only one Data Center (Application and DB tier) is activea) DC failure will lead to lengthy downtime as passive DC has to be

brought grounds upb) Low cost of ownership

Data Center Approach 2 – Active/Active Application Tiers,

Active/Passive Database Tiers

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Two or more data centers fully built up and operating independently, with only the database being active/passive.

a) Negligible recovery timeb) Higher cost of ownershipc) Delay in DB writes in one of the DC

Data Center Approach 3 – Active/Active Application Tiers,

Mostly Active/Active Database Tiers

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Two or more data centers fully built up and operating independentlya) Negligible recovery timeb) High cost of ownershipc) Additional logic to handle real time DB sync

Data Center Approach 4 – Full Active/Active

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Two or more data centers fully built up and operating independently, with only the database being active/passive.

a) Negligible switch over timeb) High cost of ownershipc) Additional logic to allocate DC to user who has already logged in

GSLB

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GSLB – Global Server Load Balancer

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1. Directing customers to the closest data center best able to service their requests

2. Making the concurrent login problem much less likely to occur3. You can personalize the experience for customers.4. You may need to restrict certain functionality based on the physical

location of a customer.5. You can roll out functionality slowly - city by city for instance6. Health checking of key components of application