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SQL Interview Success: Unlocking the Top 5 Frequently Asked Queries

 Here are the five top commonly asked SQL queries in the interviews. These you can expect in Data Analyst, or, Data Engineer interviews. Top SQL Queries for Interviews 01. Joins The commonly asked question pertains to providing two tables, determining the number of rows that will return on various join types, and the resultant. Table1 -------- id ---- 1 1 2 3 Table2 -------- id ---- 1 3 1 NULL Output ------- Inner join --------------- 5 rows will return The result will be: =============== 1  1 1   1 1   1 1    1 3    3 02. Substring and Concat Here, we need to write an SQL query to make the upper case of the first letter and the small case of the remaining letter. Table1 ------ ename ===== raJu venKat kRIshna Solution: ========== SELECT CONCAT(UPPER(SUBSTRING(name, 1, 1)), LOWER(SUBSTRING(name, 2))) AS capitalized_name FROM Table1; 03. Case statement SQL Query ========= SELECT Code1, Code2,      CASE         WHEN Code1 = 'A' AND Code2 = 'AA' THEN "A" | "A

Storage area network (SAN): Networks Vs Configurations

These are most popular terms used in Storage area networks area. Every developer must know these terms clearly. Highly useful to explain in interviews. Frequently used terminology in SAN given below for your quick reference. 

SAN Network

  • Fibre channel - Fibre channel denotes a fibre-optical connection to a device or component. This is typically abbreviated as FC.
  • Host bus adapter - A host bus adapter is used by a given machine to access a storage area network. A host bus adapter is similar in function to a network adapter and how it provides access for a machine to a local area network or wide area network. This is typically abbreviated as HBA.
  • Storage area network - A storage area network is a network of shared devices that can typically be accessed using fibre. Often, a storage area network is used to share devices between many different machines. This is typically abbreviated as SAN

SAN Configurations

  • Point to point - This is the simplest configuration. The devices are connected directly to the HBA.
  • Arbitrated loop - Arbitrated loop topologies are ring topologies and are limited in terms of the number of devices that are supported on the loop and the number of devices that can be in use at a given time. In an arbitrated loop, only two devices can communicate at the same time. Data being read from a device or written to a device is passed from one device on the loop to another until it reaches the target device. The main limiting factor in an arbitrated loop is that only two devices can be in use at a given time.
  • Switched fabric - In a switched fabric SAN, all devices in the fabric will be fibre native devices. This topology has the greatest bandwidth and flexibility because all devices are available to all HBAs through some fibre path.


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