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Raid Arrays

Discussion in 'Desktop & Laptop Computers Forum' started by General Skanky, Dec 9, 2002.

  1. General Skanky

    General Skanky
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    Been reading past posts. Only one or two people as far as I can see use Raid configurations. For a HCPC I'd say it would be a big benefit, especially if you use your pc to store media.

    I ask as I'm thinking of implementing it.

    I have 2 x Seagate Barracuda IV 80Gb drives to use. I was thinking of Striping Raid 0.

    If I have it right, the benefits will be -

    2 x 80 Gb = 160Gb drive as seen by the pc.
    Running at the optimum speed as they are both the same speed.
    Able to handle large files quickly.

    The only drawback is if one drive fails it all goes. But on my home pc it'd be the same as a single drive dying and losing the information. Just replace/reformat as applicable.

    If I ever needed to Fdisk, is it correct it will only recognise up to 64MB?? Only something I've been told. Any info on that welcome.

    So any tips on Raid? I'm really only interested in speed using these drives as they seem pretty reliable.

    Thanks.
     
  2. GavTNewbie

    GavTNewbie
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    Im no expert on RAID technology, either the software or hardware versions of it, but a guy in my work uses RAID Arrays when doing performance testing of our software and he has said the following:

    i) RAID 5 instead of RAID 0 will provide redundancy in your configuration, ie. if one disk fails, you have automatic failover of disks, but this requires more than 2 disks.

    ii) if you were prepared to halve your storage, you could setup mirroring of your drives, whereby if one disk fails, the RAID controller would be able to resume the read/write on the other disk (as both disks would contain exactly the same information). This would mean that you would only have 80GB of space, but would provide insurance if one of the disks goes down.

    Failing that, I would consider using 10,400rpm disks that are now available on the market.

    Hope this helps :confused:

    If you have any further questions, just post them and Ill ask the guy who deals with this stuff day in day out at work.

    Gav.
     
  3. General Skanky

    General Skanky
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    My mobo supports Raid 0 or 1.
    As I have two 80Gb HDD, the Raid 0 is a freebie upgrade as such. It's the speed I'm after mostly.

    Thanks for the reply.

    Can you ask your friend if it's possible to use a utility program like Norton on a Raid 0 set up please?
    Also, my mobo (Gigabyte GA-7VXP) has two IDE channels for raid, 3 and 4. Is it best to set both the HDD's to master and use a channel for each in Raid 0?

    Thank you.
     
  4. GavTNewbie

    GavTNewbie
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    I suppose it will take a while for PC Motherboards to support this sort of stuff, we really only see RAID on really high Sun Server Machines with TB's of disk space in a RAID configuration :(

    As far as Norton goes for setting up the RAID stuff, Im not sure on this :blush: as we use Sun Solaris Operating System, and the actual RAID controller is hardware driven, not software, so I would try mailing Norton support or something like this to find that out.

    "Also, my mobo (Gigabyte GA-7VXP) has two IDE channels for raid, 3 and 4. Is it best to set both the HDD's to master and use a channel for each in Raid 0? "
    -> Yes.

    Sorry that Im not much help on this.

    Gav.
     
  5. Sgt.Colon

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    Hope this helps :)

    RAID 5 - This method stores parity data across all the physical drives in the array and allows more simultaneous read operations and higher performance than data guarding (RAID 4). If a drive fails, the controller uses the parity data and the data on the remaining drives to reconstruct data from the failed drive. The system continues operating with a slightly reduced performance until you replace the failed drive.

    RAID 5 requires an array with a minimum of 3 physical drives. The capacity of the logical drive used for fault tolerance depends on the number of physical drives in the array. For example, in an array containing 3 physical drives, 33 percent of the total logical drive storage capacity is used for parity data; a 14-drive configuration uses only 7 percent.

    RAID 1+0 - Drive mirroring creates fault tolerance by storing duplicate sets of data on a pair of disk drives. There must be an even number of drives for RAID 1+0. This is the most costly fault tolerance method because it requires 50 percent of the drive capacity to store the redundant data.

    If a physical drive fails, the mirror drive provides a backup copy of the files and normal system operations are not interrupted. The mirroring feature requires a minimum of two drives and, in a multiple drive configuration (four or more drives), mirroring can withstand multiple simultaneous drive failures as long as the failed drives are not mirrored to each other.


    Note: The fault tolerance method is called RAID 1 when the number of physical drives is two, and called RAID 1+0 when the number of physical drives is greater than two.

    RAID 0 - RAID 0 provides data striping but no fault tolerance. If you select this option for any of your logical drives, you will experience data loss for that logical drive if one physical drive fails.

    However, because no logical drive capacity is used for redundant data, this method offers the best processing speed and capacity. You may consider assigning RAID 0 to drives that require large capacity and high speed, but pose no safety risk.
     
  6. General Skanky

    General Skanky
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    Thanks to you both.

    I want 'exactly' this, speed! -

    So all I have to do is set them up now and reformat and reload XP. Oh joy.:D
     
  7. GavTNewbie

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  8. Daneel

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    Is there a particular reason you want to use RAID, ie do you have a HD performance critical task you need to do?

    If not, RAID is generally a waste of time and more trouble than it is worth. This is particularly true if you don't have a dedicated RAID card, most motherboards with built-in RAID controllers have "lite RAID".

    I have never used RAID myself, although I have the option on my motherboard. I don't want the risk of loosing all my data if 1 HD dies, and also I have have 4 HDs!! One on each IDE port.

    For more on RAID I suggest you run a search on some of the following forums:

    http://arstechnica.infopop.net/OpenTopic/page?a=cfrm&s=50009562

    http://www.hardforum.com/
     
  9. dpoulson

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    Hi,

    I was until recently running an IDE RAID system using an Abit motherboard with onboard raid. I wasn't actually using hardware raid but software raid under linux because it is faster and more reliable that the onboard raid on most mobo's.

    Performance was brilliant! I've since given up performance over redundancy and am now using 2 compaq scsi arrays (7 drives in each, 1 hot swap 6 as raid 5) with a dedicated SCSI raid card. I actually saw better performance on my old 2x15Gb UDMA 100 hard drives at raid 0!

    HTH,

    Darren.
     
  10. General Skanky

    General Skanky
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    Thanks all for the replies.

    I intend to do a lot of video editing and av compression etc with downloads from Kazaa. As I understand it, Raid 0 will help it fly along.

    I'll give it a go anyway to see for myself.
     
  11. RichardH

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    You should be able to keep your existing setup when going over to RAID. I certainly managed to when I started using RAID1 (security) on my Win2000 machine. This with a Promise Mobo based controller similar to what iot sounds like you have. You have to make sure you have the RAID controller drivers installed on the OS before you convert. Have a look in the mobo manual and see what it says. Of course, if you already have stuff on the second disk, then ignore what I have said :)
    I would think that Norton etc would be OK - as the RAID is done in hardware, I think it will just be seen as 1 disk - yes, just checked in my device manager - in disk drives it just shows "Promise 1x2 Mirror/RAID1 SCSI Disk Device", rather than the 2 physical disks.

    HTH
     
  12. mjn

    mjn
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    how can you say RAID is a waste of time, yet you haven't used it yourself?

    RAID is VERY USEFUL, espically RAID 1 or 5. Fault tolerance being the greatest plus.
     
  13. 777php

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    I'm sorry to bust your RAID bubble but there has been many complaints about Seagate IV's and their horrendus performance in RAID setups. Here is a thread on anandtech.com discussing the issue.

    Anandtech Seagate RAID discussion

    You might have to send them back to Seagate for RAID capable drives. Just a heads up.
     
  14. iputerfixer

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    I've done a couple of RAID setups on Asus boards with the lite Promise raid controller.
    I had time to fool with it and this is what I found:
    Works great with Win98 and ME.
    You need special drivers for 2000 and XP setup as the drivers need to be loaded BEFORE the installation of the operating system. Both XP and 2000 give you the prompt for the F6 key to load scsi drivers, which is what promise uses.
    After that, everything loads normally and despite what some of the others have said, RAID 0 is great for large files and programs.
    If the need for disk speed is what you want, you got it.

    About Seagate having raid problems, don't know, didn't check it but I cannot believe that the hard drive would know or care whether it is on a standard IDE or Raid IDE setup.

    I still believe in partitioning the hard drive so my valuable files can be saved apart from the OS. That way I can do a clean install without much downtime.
    Usually with XP and 2000 I do NTFS on primary partions and FAT 32 on secondary. At least then I can access the secondary with DOS if I have to.

    Good luck!
     
  15. mjn

    mjn
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    true hardware raid is "invisible" to the OS, so all you need is the RAID controller driver, which as already specified, would be loaded as you're installing the OS. Once this is done, any additional HDD's/array that need to be done, are all done outside of the OS.
     
  16. General Skanky

    General Skanky
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    Well so far..............

    Raid 0 is a bit of a problem. Fdisk and reformat the drives (I use an ME bootable for this with the reformat command on it). Set up drives in Raid 0 and set up bios to allow raid. Then I downloaded from www.bootdisk.com the 6 floppys req. for XP. Did that and tried to load XP. F6 came up but asked for floppy ver. of my Raid drivers. Having a problem in being able to get it on a bootable set of floppys, only have them on cd. Downloaded the separate files from Gigabyte, it's the next part I'm a muppet on.

    Anyway. Tried that couple of times. Then reformatted with the intention to try Raid 1 (not speedy I know, but this is a steep learning curve for me on Raid). I can plonk the OS on a single drive, add the drivers then configure for Raid 1 to show it works at least. Then I'll have a chat with my computer boffin mate to work out a way to get my drivers onto floppy, to aid setting up in Raid 0.

    This is fun, my drives must the purest ones in exsistence right now. Talk about reformats, I've lost count.:D

    Thanks for the pointer. I like my HDD's, so if there should be a problem I'll just stick to separate drives in a normal IDE set up, not as fast, but I'll still have 160Gb, almost, available to me.
     
  17. GaryG

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    Hi Guy

    I've managed to avoid all this malarky for the best part of a year but when I set up my RAID (SCSI not IDE) I included the driver for the CD ROM (SCSI) on the boot floppies so that I could use the CD's. If you're using an IDE CD ROM why not set the boot drive in the BIOS to the CD and boot of the Windows CD disk ? (you'll need the original disk).

    Personally, no offence intended, I wouldn't give ME the time of day, it'a pile of crap. Unless your hardware precludes it buy yourself a xmas present and get Win2K or XP so that you can make the best use of your memory, this is especially important if you're going to be editing large files.
     
  18. General Skanky

    General Skanky
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    Hi Gary.

    I used ME as an upgrade from 98. I know it's unstable, but it has served its purpose.

    I now have XP.

    Sorting out a way to boot from CD to get the RAID drivers is the bit I'm getting wrong, hence the help from my buddy.

    I'll get there. The internet has been worth its weight in gold the last couple of weeks. Whenever a problem has come up, files wrong etc, an answer has been available somewhere.

    The reason I use an ME floppy to reformat etc is because it has more support for XP, or so a thread said somewhere.

    Anyway, I can do everything with XP 'except' the Raid 0, but that's temporary. Even if I have to crowbar the drives into a raid setup I'll get there.:rolleyes: :D
     

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