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Thread: compact flash raid

  1. #1
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    compact flash raid

    well I have been thinking of a way to get really fast boot times in windows. It seems compact flash cards work well for cheap flash storage, but they seem to really lack speed. What about using a promise raid card and 4 ide compact flash adapters (here )? the seek time of the compact flash would be almost 0, and the speed should be quadrupled (or you can even get a 6 drive raid card). Does anyone know why this wouldn't work? You can find fast Sandisk flashdrives on ebay these days pretty cheap, I think they are faster than regular compact flash.

    It wouldn't be cheap ($175 for about 4 128mb compact flash cards). But it should be a lot quicker than other flash solutions.

    the fastest compact flash I can find is around 3.6mb a sec (24x), and the sandisk flashdrives will do around 16mb a sec burst.
    sv24, 733mhz celeron, 80gig hd, 5.6" MA Audio tft, x10 remote, RF Keyboard.

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    I read somewhere that compact flash and other similar memory devices can't take the read/write that system type memory can. Meaning shorter life span for the memory modules.

    Someone else may be able to elaborate better than I can.

    Disk on Chip (DOC) is of a differant design and can handle such things. I personally don't know much about it though...

    -Mario

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    DOCs work well, but they are VERY expensive. The best way to go would probably be to get 4 128-192 meb Sandisk Flashdrives. they range from $40 to $80 for 192mb on e-bay. They are flash memory ment to be used as harddrives. If I had a job now I would buy 4 and test my little theory out Does anyone here have windows installed on a compact flash card?
    sv24, 733mhz celeron, 80gig hd, 5.6" MA Audio tft, x10 remote, RF Keyboard.

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    I will try to find the article that showed flash memory as found in compact flash don't have the duty cycle required.

    This however may change from one manufacturer to another...

    -Mario

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    Here are a couple articles from the web site Digital Photagraphy Review that are related to this post:

    This is a forum posting asking about the life span of a CF card:
    http://www.dpreview.com/forums/read....essage=1337826

    This one is an article measuring the speed of many CF cards and two IBM microdrives:
    http://www.dpreview.com/articles/med...re/default.asp

    -Brandon

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    You could do that, and it would probably increase your speeds, but by what? a few seconds? Booting off compact flash shouldn't be any slower really than booting off a hd, it makes up what it lacks with transfer speeds with the seek time. And Compact Flash has a limited Write/Erase life cycle. You can read from it how ever many times you want, but you can only write/erase it a certain number of times.
    -Nick

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    booting off compact flash is already much quicker because of the low seek time, I am just trying to get it even faster I already know of the limited read/write cycles, but people of this forum have been booting of off Compact flash cards for months without any problems. Anyway, my new plan is to get 4 sandisk flash drives off of e-bay. They are faster and they are ment to be used as flash harddrives. Unfortunatly it is going to take a while until I get enough money to do this, but hopfully it will happen within a month or so.
    sv24, 733mhz celeron, 80gig hd, 5.6" MA Audio tft, x10 remote, RF Keyboard.

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    it's funny, a few weeks ago I had the same idea but didn't post about it.

    Oh FYI if you use windows 2000/XP you can just use software raid, no need for the controller .

    However you won't get 4x the speed because IDE busses are on a master/slave relationship. Both drives cannot be transferring data at the same time on the bus, so you'll only get 2x the speed (at least this is about what I have found in practice). I once set up a 4x40GB raid array with the highpoint mobo controller and was really dissapointed in the speed, it was not much faster than my 2x raid array that I had before it. Then one of the drives died so I had to get it replaced and didn't bother putting the raid back together. You will see a bit higher than 2x with 4 hard drives because the slaves can transfer data while the drives are seeking to the next location, but I doubt that you'll get > 2x the speed with a 4xCF array due to the 0 seek time unless you have 4 seperate IDE busses and put all 4 CF cards as masters.

    I'm not concerned about the limited number of write cycles because these drives are not really to be used for much writing at all. I was thinking of a setup with 2x256MB CF raid which you can use to host the OS and applications, and then have 2 laptop hard drives in a raid for all of the things that get modified frequently. Then you get best of both worlds. And besides, you get somewhere around 50,000 write cycles. "50,000 write cycles should be enough for everybody".

    Additionally you almost certainly are going to have a hard drive alongside the CF card (where you gonna put all that music?) so anything that needs to be modified frequently can stick in there.
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

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    If he's going to go that far out, he might as well do a hardware raid card, which will give hime 1 device per channel (3Ware, Adaptec, Promix SX6000).
    -Nick

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  10. #10
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    but why get the good hardware raid cards when you don't need to? they're not cheap...
    IN DEVELOPMENT -- '96 Mustang, lilliput with PII/450 laptop, custom DC-DC power supply, 60GB; Garmin GPS; 802.11g; compact keyboard, small graphical LCDs, OBDII.

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