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Showing posts from March, 2017

Simple Storage Service-S3

AWS is revolutionizing  many aspects of the lively hood of many folks in the tech industry. Industries have aligned its processes around the many AWS services and depend on the availability and consistency of its services. As a data person , I am supper delighted and totally on board the AWS journey to a brave new world in the cloud. For those of you who are getting on-board AWS, Simple Storage System(S3) will be one place to start the journey. I have outlined few points on S3 that can help you on your way. Is Read after write consistency for PUTS for new objects Is known as object based storage Default S3 buckets per account  =100 Storage tiers S3 Durable , Immediately available , frequently accessed S3-IA Durable , Immediately available , infrequently accessed S3 - Redundancy Reduced  redundancy storage ( data that is easily reproducible , such as thumb nails ,watermarks etc. ) 99.99 vailability Glaciar Cheaper than ...

The impact of CDC To a Async node

Recent as late last week, I ran into a baffling situation where a async node in the MsSQL HA  solution was not in sync for few hours. Eventough, the high watermark kept increasing for the synchronization between the primary and async node's the latency kept increasing significantly. By the way , HA solution is in AWS in and the nodes are multiple regions. The impact of having a node not in sync - Transaction log on the primary will blow out to be uncontrollable - CDC (Change data capture ) will not work The impact to the transaction log is quite known fact, but what caught me off guard was the impact to CDC. It was later that it occurred that CDC consumes the transaction log agent, and the transaction log agent does not process the log records until they are  harden at all the HA nodes in the availability group. This lead to more concerns on what needs to be done in case of  catastrophic situation ie. When the primary node in a HA configuration is compromised a...