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Tech Tips, Tricks & Trivia

by 'Anil' Radhakrishna
An architect's notes, experiments, discoveries and annotated bookmarks.

Search from over a hundred HOW TO articles, Tips and Tricks


This Week I Learned - Week #284

Sunday, September 16, 2018
This Week I Learned -

* Microsoft-provided tools Azure Site Recovery Capacity Planner and Azure Site Recovery Deployment Planner can help you analyze your source environment and compute requirements for the target environment.

* The Azure Site Recovery Deployment Planner can be run without having to install any ASR components in your on-premises environment. The tool does not impact the performance of the production servers, as no direct connection is made to them. All performance data is collected from the VMware vCenter Server/VMware vSphere ESXi Server which hosts the production virtual machines.

The ASR Deployment Planner has three main modes of operation:
- Profiling
- Report generation
- Throughput calculation

* Azure Site Recovery Deployment Planner is available for both VMware to Azure and Hyper-V-to-Azure production deployments

* Uber ride can get you picked up at more than 300 airports

* Uber gathers trip data in more than 500 cities across the world. Uber Movement uses Uber’s aggregated data to help urban planners make informed decisions about our cities. It helps discover patterns and analyze the impact of events, rush hours, and road closures worldwide.

Uber operates in 35+ cities in India

* "It was almost normal for people over thirty to be frightened of their own children." - George Orwell 1984, chapter II

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Amazon S3 vs EBS vs EFS

Saturday, September 15, 2018
Comparison chart from the NetApp blog with additional notes -

Features Amazon S3 Amazon EBS Amazon EFS
Purpose static storage service useful for static website hosting, media distribution, version management, big data analytics, and archiving persistent storage device that can be used as a file system for databases, application hosting and storage, and plug and play devices works like NAS devices and performs well for big data analytics, media processing workflows, and content management. excellent as a managed network file system that can be shared across different Amazon EC2 instances
Storage Cost (US-East, for example) Cheapest cheaper than EFS but can only be accessed by one Amazon EC2 instance at a time which can be problem in a clustering or distributed app 10 times more expensive than Amazon EBS
Storage Size No limit on number of objects Maximum storage size of 16 TB No limitation on the size of the file system
File Size Limitation Individual Amazon S3 objects can range from a minimum of 0 bytes to a maximum of 5TB No limitation on file size in EBS disk Single files have a maximum size of 47.9TiB
Data Throughput and I/O •Supports multipart upload. It is recommended for capability of objects larger than 100MB
•The largest size of a single object uploaded using PUT API can be of 5GB
SSD- and HDD-backed storage types
•Use of SSD backed and Provisioned IOPS is recommended for dedicated IO operations as needed
Default throughput of 3GB/s for all connected client
Performance •Highly scalable managed service supports 3500 PUT/LIST/DELETE requests per second
•Supports 5500 GET requests per second
•Manually scale the size of the volumes without stopping instance.
•Baseline performance of 3 IOPS per GB for General Purpose volume
•Use Provisioned IOPS for increased performance  
•Highly Scalable Managed Service
•Supports up to 7000 file system operations per second
Data Stored •Stored data stays in the region.
•Replicas are made within the region in multiple availability zones
•Amazon S3 objects can be copied to other region using the cross region replication feature
•Data stored stays in the same Availability zone.
•Replicas are made within the AZ for higher durability
•Data stored stays in the region.
•Replicas are made within the region
Data Access Accessible over internet based on access policy configured Can only be accessed by a single Amazon EC2 instance Can be accessed by 1 to 1000s of EC2 instances from multiple AZs, concurrently
File Permissions/ File System •Can be mounted as a file system, but it is not recommended
•Unlike traditional file systems, bucket permissions do not pass on to the folders by default (bucket policies can be used to achieve this)
Supports various file systems, including ext3 and ext4 •Auto-Scaled File storage service for use with AWS EC2
•EFS can be used as network file system for on-premise servers too using AWS Direct Connect.
Supported Encryption Mechanisms Server Side Encryption with Amazon S3-Managed Keys (SSE-Amazon S3),AWS KMS-Managed Keys (SSE-KMS), and with Customer-Provided Keys (SSE-C)
Client Side Encryption using an AWS KMS–Managed Customer Master Key (CMK) and using a client-side master key
Uses an AWS KMS–Managed Customer Master Key (CMK) and AES 256-bit Encryption standards Uses an AWS KMS–Managed Customer Master Key (CMK) and AES 256-bit Encryption standards
Access Control •Using bucket policies and user policies
- Managed with ACLs
- Pre-signed URL access based on IAM
•Security groups
- NACL
- User based Authentication such as IAM
•Security groups
 -User-based authentication
- IAM 
Availability 99.99% availability of objects over a given year 99.99% available Highly available (No public SLA)
Availability Zone Failure Can withstand up to two concurrent AZ failures Cannot withstand AZ failure without point-in time EBS Snapshots Every file system object is redundantly stored across multiple Availability Zones so it can survive one AZ failure.
Durability Eleven 9’s of durability
(99.999999999%)
20 times more reliable than normal hard disks Highly durable (No public SLA)
Eventual Consistency Problem AWS Amazon S3 offers eventual consistency for overwrite PUTS and DELETES in all regions. No such issues No such issues

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HOW TO use a Bookmarklet on Chrome mobile

Thursday, September 13, 2018

Web Performance guru, Steve Souders, has nicely listed the steps to use a bookmarklet within a mobile browser (generally deemed not possible as mobile browsers lack a bookmarks bar like desktop browsers do). His technique involves bookmarking a URL with an embedded anchor and then editing that URL within the mobile browser
While using those instructions on Chrome on Android, I had to do the last step differently to make Steve's Mobile Perf Bookmarklet work. I had to type the bookmarklet by name ("Perf" in my case)  in the address bar to invoke while I was on the web page where I wanted to use the bookmarklet.

Surprisingly, the Mobile Perf bookmarklet doesn't work on some webpages (like Google Search) & I haven't been able to figure out the reason. It also appears that only certain type of bookmarklets can work on mobile browsers.

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Treacherous 12 Threats to Cloud Computing

Tuesday, September 11, 2018
According to the Treacherous 12 Threats to Cloud Computing report compiled by the Cloud Security Alliance (CSA) Top Threats Working Group, following are the 12 critical issues to cloud security:
1. Data Breaches
2. Weak Identity, Credential and Access Management
3. Insecure APIs
4. System and Application Vulnerabilities
5. Account Hijacking
6. Malicious Insiders
7. Advanced Persistent Threats (APTs)
8. Data Loss
9. Insufficient Due Diligence
10. Abuse and Nefarious Use of Cloud Services
11. Denial of Service
12. Shared Technology Vulnerabilities

The 60-paged report also includes 21 anecdotes and examples

This Week I Learned - Week #283

Friday, September 07, 2018
This Week I Learned -

* Azure ML Studio supports:
- Classification
- Regression
- Clustering
- Anomaly Detection
- Recommendation
- Ranking

Google Vision API code samples include scripts written in PowerShell

Two versions of the Azure Functions runtime are available. The 1.x runtime is GA. It's the only runtime that is approved for production applications. The 2.x runtime is currently in preview, so the languages it supports are in preview.

$req and $res are Azure Functions-specific automatic variables. The body of a HTTP POST request ends up in $req. Azure Functions returns the contents of $res

National Geographic has a 3-minute beginner level tutorials on a wide variety of topics in its 101 Video series

* Giving alms to beggars or buying articles from hackers/vendors at intersection is a traffic offence under 22(a) RRR/177 MV Act

* Entrepreneur & IIT-ian, Sanjiv Saraf is the founder of Rekhta Foundation which has established the free website Rekhta.org with the objective of promoting and disseminating Urdu literature

* US has 4 time zones while India (with a width of about 3000kms) & China have one.

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