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  1. #1

    Arrow RAID-1 Mirroring

    I am looking into building my own server running RedHat Linux 7.2 and Plesk 2.5 for colocation purposes. I am interested in adding support for RAID-1 mirroring with a controller card. I'd rather do it with hardware since it's really just as simple as adding the card, making sure Linux see's my RAID card (via the driver) and plugging in the hard drives. No other configuation would be neccessary.

    However, I've never used a RAID-1 controller card on Linux before.

    * How do I know if one drive has failed in this type of configuration?

    * Is there some kind of software that comes with the controller card that will allow me to run status checks on the drives?

    * And lastly, any recommendations on choice of hardware or how to implement a RAID-1 configuration on a RedHat Linux system?

    Any help is appeciated!

    Thanks,
    --Steve

  2. #2
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    Re: RAID-1 Mirroring

    Originally posted by steve93138
    * How do I know if one drive has failed in this type of configuration?
    Depends on the card. If you're talking high-end SCSI RAID cards, you'll generally have some kind of a diagnostic utility that'll run under Linux and can query the card to find out the status of the array.


    * Is there some kind of software that comes with the controller card that will allow me to run status checks on the drives?


    Again, depends on the card.


    * And lastly, any recommendations on choice of hardware or how to implement a RAID-1 configuration on a RedHat Linux system?


    Do you want SCSI or IDE? How many drives? Are you really sure you need a hardware-based solution? Linux's software-based RAID is quite mature.

  3. #3

    Re: Re: RAID-1 Mirroring

    Originally posted by amaroq
    [BDo you want SCSI or IDE? How many drives? Are you really sure you need a hardware-based solution? Linux's software-based RAID is quite mature. [/B]
    I'd like to be able to get away with 2 40GB 7200 RPM drives. But if there is any reason to go with SCSI other than a somewhat faster speed, I'd go for that.

    I haven't really researched Linux's software-based RAID vs hardware RAID all too well yet, but if plugging a card in and attaching drives is the easiest way to go, I'd rather just stick with that even if it costs an extra $150.

    I also know that I could get a motherboard with built-in RAID support (IDE), but RedHat may or may not have drivers for it so I'd rather not go that route. It might also be nice to be able to reuse the RAID card on some other system should I need to do so down the road.

  4. #4
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    Re: Re: Re: RAID-1 Mirroring

    Originally posted by steve93138
    I'd like to be able to get away with 2 40GB 7200 RPM drives. But if there is any reason to go with SCSI other than a somewhat faster speed, I'd go for that.
    Probably not. As long as you're buying high-quality drives you're not going to take a hit in reliability, and unless you're doing something with a lot of small non-sequential reads/writes to the disk, you'll probably not notice much difference.



    I haven't really researched Linux's software-based RAID vs hardware RAID all too well yet, but if plugging a card in and attaching drives is the easiest way to go, I'd rather just stick with that even if it costs an extra $150.


    If simplicity of installation is important, then you'd probably be better-off going with a hardware-based solution. Setting up software-based RAID under Linux isn't extremely hard, but it's not extremely easy either.


    I also know that I could get a motherboard with built-in RAID support (IDE), but RedHat may or may not have drivers for it so I'd rather not go that route. It might also be nice to be able to reuse the RAID card on some other system should I need to do so down the road.
    Be wary of mainboards with built-in RAID "controllers". They're generally software-based, until you get into very high-end server boards (Supermicro makes some boards with built-in SCSI that have add-on RAID "plug-in" modules, for example), so you're not really gaining anything that way -- performance is based largely on the CPU load, and they're generally not very refined in terms of drivers and whatnot.

    It sounds like what you want is probably a card from 3Ware (www.3ware.com) or ArcoIDE (www.arcoide.com), or maybe from Adaptec (www.adaptec.com) if you want a 3Ware-like controller -- I've never used one of Adaptec's IDE RAID controllers, so I can't comment on them.

    ArcoIDE's controllers are OS-independent; they basically just act as a "translator" between the disks on one side of the controller and the IDE controller on the other side, balancing reads and writes and making sure both disks are still functional. They're expensive and only two-drive models are available, but they're about as simple as you can get, and performance is decent.

    3Ware's cards are more like an IDE version of a "real" SCSI RAID card. They behave like a real RAID controller -- the controller acts to the OS as if it were a single SCSI drive (your RAID'ed IDE disks are accessible as /dev/sd*), and it detects the drives' capabilities and adjusts itself for ideal performance automatically. The controller is configured by a built-in BIOS management utility -- you choose what disks you'd like in the array, what kind of an array you'd like (RAID-0 or RAID-1 on two-port cards, as well as RAID-5 and RAID-10 on four, eight, and twelve(!) port cards), and it formats the array for you -- pretty standard stuff. I don't know much about 3Ware's management utility under Linux, as I've never had occasion to use it intensively.

    Depending on what you're looking for (ease of use vs. more features, etc.) one of these is probably what you're looking for. If you're not afraid to recompile the Linux kernel if you have to (3Ware's drivers are probably compiled into the kernel in a standard RedHat distro, though I can't say for sure since I don't use RedHat) and you think you could use a little more flexibility, 3Ware's cards are probably the way to go.

  5. #5

    Thumbs up Thanks for the help, amaroq!

    While the OS Independant solutions from ArcoIDE would be my first pick, I see that the only way to know if a drive is malfuntioning is to manually look at the indicators. This means it's not ideal for colocation. Bummer...

    But all is not lost, I checked out the RAID solutions from 3Ware and they are quite good. As a matter of fact, I found their DUAL IDE solution for just $130 online. Not bad. They also seem to work with all the latest versions of RedHat Linux.

  6. #6
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    I've heard good reviews of Promise and 3Ware raid cards.

  7. #7
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    and I quote...

    "Trying to build a RAID array out of IDE drives is like auto racing Yugos. Sure, you can do it, but it doesn't impress anyone and it's not very fun to watch."
    - David McNett


    words to live by.

    -neil
    Last edited by neil; 07-27-2002 at 05:47 PM.
    neil MCITP, VCP

  8. #8
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    No offence but I am guessing that quote is old as hell, cos we run some big-ish RAID 5 arrays from IDE and have never had a problem - and I can tell you that it doesn't perform like a Yugo, the arrays we have fly along.
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  9. #9
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    Originally posted by neil
    and I quote...

    <snip>

    Just 'cos someone says it doesn't mean it's true.

    Don't forget that IDE drives have made some great leaps forward in terms of performance and reliability in the last couple years, along with the availability of previously-non-existent quality IDE RAID cards. Sure, if you've got lots of cash to spend SCSI's going to be your better bet, but if you don't...

  10. #10
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    Don't forget that SCSI drives are just IDE drives with an onboard device controller chip - most of the technology is the same.

    Companies like 3Ware would not build their entire business on the concept of IDE Raid and still be around if it didn't work and didn't perform.

    And Adaptec, obviously a leader in SCSI, would not have followed 3Ware into the IDE RAID market unless they were feeling a pinch and a need to service that segment.

    7200 rpm modern IDE drives on IDE RAID easily outperform older SCSI drives that we considered "super fast" just a few years ago.

    and guess what - those drives are still up and running in a LOT of older Unix and other servers.

  11. #11
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    :: shrug :: yes it is an old quote - just thought it was funny. I've always perferred scs raid - however I haven't dealt with IDE raids for a couple of years.

    Certainly IDE is much much inexpensive.
    neil MCITP, VCP

  12. #12
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    My only advice would be to avoid the promise onboard controllers, as they only have drivers for a limited number of OS's: like RH and open linux. At least the promise that I have.

    Regards,

    Jeff

  13. #13

    Question fault-tolerant

    I read somewhere that the Promise controllers are not "fault-tolerant". Anyone know what that means?

  14. #14
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    Ive had bad experiences with tyan with built in promise controller - do some research on linux and promise - promise keeps their drivers closed - you may even have to use an older version of the kernel to get support unforunately our tyan board had it built in. bummer, we had to use the spare ide slot (only 1 for cdrom) to connect 2 hds and cdrom - its not ideal because we would have setup software raid (which works just ask well as hardware) on each ide bus, but no they are all on the same bus, and if the bus blows... well - lets not talk about that.
    Avi B

  15. #15
    Originally posted by spiv
    Don't forget that SCSI drives are just IDE drives with an onboard device controller chip - most of the technology is the same.
    Don't you believe there is a reason why nearly all professional servers utilitize SCSI? Exceptions: cheap webosting, some storage devices, very small workgroups servers.

    And Adaptec, obviously a leader in SCSI, would not have followed 3Ware into the IDE RAID market unless they were feeling a pinch and a need to service that segment.
    That's capitalism They will serve every segment to make more money.

    7200 rpm modern IDE drives on IDE RAID easily outperform older SCSI drives that we considered "super fast" just a few years ago.
    A few years in this industry are ages. Would you compare a 2002 car with one 50 years ago?

  16. #16
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    New IDE drives are starting to give SCSI drives a run for their money in a lot of segments now, every generation they close the gap a little more on SCSI drives. When you're talking RAID arrays, the read speeds pretty much become irrelevant as once you get a few drives on a controller you're going to saturate the PCI bus anyway, move to 64bit PCI, and you're talking a few more drives and you've got it saturated again.

    Most of the doubters and detractors of IDE RAID are people that have never even used it.
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