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Thread: compact flash raid

  1. #11
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    Originally posted by Telek
    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.
    I may be wrong, but you can not use 2000 or XP software RAID on the boot drive.

    Also I thought the software RAID feature only came with 2000 Server.

    Again, I could be wrong...

    -Mario

  2. #12
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    It can be done but it's tricky... Depends how much space you want to loose.

    I guess doing that on CF cards is probably not the best idea due to limited space. Basically what you do is make a small normal partition at the start of the hard drive, just enough to load drivers to mount the NTFS RAID partition, and use symbolic links for the rest of the files on the startup drive. You can get it down to 16 megs or so I think. What I did was make a system partition that was 5GB at the start of the drive, then that partition was mirrored to the second drive. The remaining 35GB on both drives was setup as a striped raid.

    You can use RAID on windows 2000 pro and windows xp pro but depending on the type of raid you might need some special tools to do it. You cannot do RAID 5 in software without the server version, but striping and mirroring is possible.
    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.

  3. #13
    Jay
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    This might be of some use. Iíve decided against it, I like the hibernation concept better. Itís faster than any boot cycle (including all programs loading).

    http://www.m-sys.com/content/product...descsi&FAM=FFD

  4. #14
    Jay
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    Sorry. This one is the IDE version. The other one is SCSI

    http://www.m-sys.com/content/product..._25_35&FAM=FFD

  5. #15
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    Weren't those the $2 a mb drives discussed the other week?
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  6. #16
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    no the $2/mb drives were up to 5GB ... these are much older models.
    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.

  7. #17
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    You can get a 192meg Sandisk flashdrive for about $60 on ebay Here . four of those for around $250 and you get 768 megs of super fast no-seek harddrive space. PLus they are ment to be hardrives, so they are much faster than cf cards, and they don't have a problem with reading and writing to them many many times .

    MTBF (Mean Time Between Failures) >1,000,000 hours
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  8. #18
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    Data Reliability <1 non-recoverable error in 1014 bits read
    Wow that sucks...

    (I think he meant 10^14 not 1014.

    Endurance 300,000 write/erase cycles
    Not bad! That's actually several years even if you use it as a normal hard disk.

    Data Transfer Rate to/from Flash 4.0 MB/sec burst.
    Data Transfer Rate to/from Host 6.0 MB/sec burst.
    There is the problem really. You're looking at a max of 4.0MB/sec (and that's burst)... So even if you had a proper raid controller with 4 seperate channels you'll still only see a max of 16.0MB/sec.

    Which is why a normal hard drive with hiberate is about the same. Since hibernate uses a contiguous file on the hard disk to store memory, I can boot my system (with 256MB... you really don't need more than that in a car) with all applications already loaded in about 20 seconds past post. You're not going to be able to boot XP even from a flashdisk in 20 seconds, nevermind including loading all the applications, etc.

    But it'd still be supercool to have a 4xCF raid... very low power too which is nice, and a lot more durable than a hard driive.
    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.

  9. #19
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    btw the promise raid cards aren't really raid its software raid that is built into the drivers for the OS otherwise they're just ide controllers
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  10. #20
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    That's not entirely true.

    The Promise Raid cards to a limited amount of hardware raid, but not much... This is shown by the fact that you can boot off of them into DOS or Linux without the need for drivers... It's just supported via Int 10... If you want DMA access then the drivers have to handle it because the card doesn't do that).

    You can however install windows 95 or 98 without the raid drivers and it will still work fine. Just not optimal, but if the devices that you are using are PIO mode only (most CF cards are, this is a BIG detraction from using CF) then you don't really need the drivers.

    Plus the promise cards are great because you can buy the cheap one and with 1 resistor convert it to the expensive one! I bought a Promise 66 a while ago and it shortly thereafter became FastTrack66 with the addition of 1 resistor.

    It is only 2 channels however, the 4 channel promise cards (just like any other 4 channel card) are very expensive, hence why I wouldn't suggest getting them.
    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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