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Is there a way to use multiple SD-memory cards with the Raspberry Pi, perhaps in RAID 0 configuration? It would be a good way to expand the available memory, reuse some of extra the cards that I have, and keep the Wattage low (compared to an external drive).

  • You could use a SD-card-reader and just plug it into the USB port. – Gerben Oct 9 '13 at 12:59
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there's only one SD slot on the Raspberry Pi, so you'll need some external hardware, and as far as external hardware goes, you cannot beat a good HDD with a pack of old and faulty flash cards.

and regarding the power consumption, contemporary 2.5" HDD consumes about 0.15-0.2A on average, that's about 1/4-1/5 of what your Pi consumes, you can hardly go any lower than that using powered USB hubs and all this stuff you'll need to access your SD reader cards.

  • Actually electric power is defined in watts (W), which can be expressed with current and voltage. Eelctric power formula for DC current is: P = I x V. So, if we go to your example: Rpi consume ~0.2A@12.5V_DC (2.5W) and external USB 2.5 " HDD consume about 1.25A@12V_DC (15W). – TomiL Oct 17 '13 at 8:30
  • @TomiL your numbers are way off, there are no 12V anywhere in the Raspberry Pi. Also, I wonder where did you find 12V in the USB (5v powered) device. Use Google, it should help. – lenik Oct 17 '13 at 23:34
  • my numbers are taken from the website provided in my link(from www.raspberrypi.org).The alexeames was using 3x LiPoly (so this is where 12.5V is comming from!),consider 90% efficiency of switching regulator he used, we get 0.45A@5V_DC on Rpi's input power line.As we know, the external HDD can't be directly powered from Rpi's USB (providing only ~140mA/USB port), so also ext.power supply for ext.HDD is needed.In my case those were in 95%(of all HDDs I ever had) on 12V DC adapter.This is the thing I was trying to say:specify current AND voltage. :) – TomiL Oct 18 '13 at 8:25
  • Btw, 0.2A on USB2.0 bus means only 1W of power, which is really just average power consumption for portable USB HDD (not flash!) and when we consider most of the time is idle mode or similar (low energy/sleep/low spin). Btw, most PC/laptop 2.0 USBs are capable of providing >500mA of power as standard says! This is way we are able to run portable USB HDD on only 1 port. And YES, I agree with you regarding comparison between 2.5" HDD and old and faulty flash cards. ;) – TomiL Oct 18 '13 at 8:30
  • A typical 2.5" 5400rpm HDD will require about an amp of five vijayjay to spin up. That's five watts, and if you're not careful, I guarantee that you will damage that sensitive device of yours. You could stagger that spin-up with some (nice, chunky, like you might find in a camera flash) capacitors. Another option might be to power the drive externally, though there are implications regarding standard compliance if we explore the wrong avenues in that case. – autistic Oct 21 '17 at 19:25
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Software RAID

In relevance to this Super User answer.

You can get a whole lot of SD to USB adapters because there are no multi SD port readers. Then you set up raid in Linux or use ZFS on the SD Cards

4 Ports SD to SATA Adapter

Runs in RAID-0

You will need to use a SATA to USB to use this.

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CF Interface

Runs in RAID-0

You can get a CF to USB convertor.

enter image description here

-1

1. solution: USB style

Is your attention only to extend program memory? Then, as @Gerben already said, buy/use USB SD-card reader. But than you don't need RAID 0 configuration. It is meant to be for improving performance while using data striping, but major drawback is fault tolerance: if one element in array dies, whole array is corrupted.

2. solution: network style

One solution could be to search for any (free) hosting, like ftp, http, etc. Then just copy user data to web storage. Or use your own server, like wamp. You can use ethernet or USB (e.g. USB WiFi dongle, USB Bluetooth, etc.).

3. solution: GPIO style

There are also some GPIO pins already on the board with various protocols: UART TTL, SPI, IIC. Those can be directly connected to other external devices via TTL pins.

So, the only limitation is your imagination ;)

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