XigmaNAS

I am looking forward to buy some hardware component like pen drive, external hard disk. I really wanted to know that whether I should buy it online from any market places like Amazon or Flip kart or should buy it directly from physical shops.
Which would be cost effective for me?

in Germany ; ALTERNATE is a good option: https://www.alternate.de/

What exactly will you be using your pen drive for? It might be better to go for a low cost ssd instead.

I think Amazon :/ Btw. Guys! I wanna use Home inverter for my pc because double battery ups not enough due to heavy light cuts in my place in summer https://invertero.com/ And multiple battery ups like APC is cost equal to inverter which can give more backup. So is it safe to use Inverter for gaming pc?

most PC power supplies are happy over a wide range of voltage
12 VDC is not the most efficient source for an inverter most commercial users are at 48V
if the mains power is often down you will need a lot of battery irrespective of what voltage you choose
if you choose a ups with many extra batteries go for an "always on" double conversion type
where the inverter is designed for continuous duty