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Storage expansion

posted 22 Feb 2013, 15:05 by Flip Pipe   [ updated 20 Mar 2013, 02:21 ]
One of the project objectives is to have more storage space. Why? Because compact flash drive space cost 3x more than usb.

Lets compare:

 Sandisk Cruzer Switch USB 2.0 Flash Drive - Black + Red (32GB)
 SDHC SD Memory Card - Blue (32GB / Class 10)
 Transcend 400X 32GB Compact Flash

I think Compact Flash card are used in DSLR because the have a high throughput: 167MB/s, in contrast with 25MB/s of the SHDC (check wikipedia)

Acording DealExtreme, the USB pen I show only writes as 10MB/s (which I think it is the normal in this small size), the SDHC is 14MB7s. They don't have information about the CF card, but if this card was 133x, would have a throughput of 25MB/s... being at 400x, it should read/write a littler fastest.

By the way, USB interface goes up to 60 MB/s.

After the machine empty the buffer to the CF card, this features of the CF cards it is no more necessary, so, why not to add more space, but cheaper.

In Raspberry Pi, there are two options... or a big SC card... or lots of usb flash drives connects through an hub. So, the idea is to join several usb flash drives in a hub:

  or      or else       with this  

After join this pieces, is join all storage space in a raid... with usual HD is simples.... but with usb flash drives will also sem simples with this site:

Then the next step is to choose the right raid level. If I buy 4 usb flash drives of 32GB:

Raid 0; 128Gb and write gains... but if one drive fails, all information goes to garbage.
Raid 5: 96GB  without performance gains... but if one usb flash drive fails, the data (out precious photos) remain intact.
Raid 10: 64GB of storage and double the write speed and I could lose a pen.
Raid 1: This is almost excluded... just 32Gb and no performance gain.

Later, I will do some tests and choose one of them.