RAID of SD cards?
prof_braino
Posts: 4,313
Has anyone tried making a RAID out of SD cards? I imagine a prop could listen to a host, and receive a data stream and spit this out to an SD. The serial transfer rate is a little slow, but if there were two SD cards, the transfer could be twice as fast, if done in parallel like a striped RAID. And each time we double the number of cards the transfer rate doubles. If we could use 8 cards in a striped array, it might be 8 times as fast as a single card and 8 times larger. At $5 each an array of 8 cards of 4 gig would be $40 for 32Gig.
Too goofy? Your thoughts?
Too goofy? Your thoughts?
Comments
you are already on the list. Me and MacTuxLin did not wanted to talk about it before the KITs ready for sale and evaluation.
But since you ask - yes RAISD(TM) QS-KIT is allmost there for the Prop. 4 SDcards + RTC + thru-hole parts to solder as add on board for the QS.
but don't tell anybody ...
Enjoy!
Mike
Your secret is safe with me. All I can say is Baw Ha Ha! This is going to be COOL!
Inside I found http://www.msrobots.net/raisd-qs-kit.aspx
And newegg has 32Gb micro SD class 4 for $19, or 8Gb for $6
Ferb, I know what we're going to do today!
Thanks msrobots! This is going to be cool!
Yes, finally I was able to upload all code needed.
Real work is hindering me to play with the propeller...
MacTuxLin produced the boards and provided soldering Instructions. Please be aware that you need some insulation between the back of the prower-regulator and the board if you want to lay it flat.
As soon as I am of work today I will extend the documentation.
The RAISD QS-KIT will be available at www.propellerpowered.com.
Enjoy!
Mike
You could then power both the server (RAISD-QS) & client (e.g. PPB) with a wall-wart.
This is very funny!
wow. Your prototype looks impressiv.
Kenichi already had a 4 sdcard board - he build the prototypes I used for development.
As ar as I can see you should be able to run my software on your board and vice versa.
This is COOL,
We have now direct replacements for Fat_Enine and FSRW using the cards as array.
see http://www.msrobots.net/raisd-qs-kit.aspx .
Enjoy!
Mike
What application are you using this for? Did you use SPI mode or did you start in on 4 bit transfer?
The reason for the breadboard was to try sharing some of the SD card control lines.
I'd like to eventually digitize lots of my old vinyl records and have a propeller jukebox that can store and play them back. A project like that could benefit from faster read and write, and it also could benefit from larger capacity of multiple SD cards. With 4 32 gig cards, you're getting into serious storage!
I did look into 4 bit mode but as far as I can tell, writing in 4 bit mode requires that each of the 4 bitstreams generate its own CRC, and that seemed like a lot of work for a propeller to do.
I want to figure out if SPI mode is enough, or is 4 bit parallel mode would be an advantage.
Could a prop even use or keep up with 4 SD using 4 bit mode?
funny thing is that you can read the checksum (RAIS Server uses this to compare sectors) without needing them for write access.
calculating a checksum for each bit will slow down everything. and there is some licence needed for 4-bit access to sd cards.
The only thin running in SPIN on the RAISD Server is the Serial User Interface.
Everything else is done in PASM so it uses allmost all the power a P1 can give.
But still one cog left and about 2000 long hub ram ...
I do have some application allready on my workbench...
Enjoy!
Mike
As I understand it, we can USE any 4 bit mode we want, but we can SELL any 4 bit mode applications, is this correct?
What if we were slimy as a patent troll and did a two bit or three bit transfer (and just didn't use the remaining lines)?
What is we called it 12 bit mode, since it goes across 3 cards?
It is more complicated then that, you do not even get the description of the 4-bit mode without beeing member of th sd-card-group.
But using the 6-wire interface of RAISD Server and RAISD client you can transfer pretty fast between the Props. And the RAISD server can read 4 sectors at the same time a single card can read one sector...
Basically the RAISD server is a fast block-driver with 16K cache.
if you look at the speed-test results at http://www.msrobots.net/raisd-speed.aspx you can see that as allways SPIN is slowing things down at the filesystem-level.
I needd to look for some file-system/FAT code in PASM. Michael Park has some in SPHINX as far as I remember.
It would be pretty cool if we could use the RAISD System with a FORTH client. By now we have replacements for Fat_Engine 3.0 and FSRW 2.6 for the client side..
Jeff from www.propellerpowered.com should receive the missing insulators for the regulator soon (mine arrived yesterday) so the RAISD QS-KIT should be available there soon.
Enjoy!
Mike
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Jeff