Raid - anyone got any experiences?

Discussion in 'Desktop & Laptop Computers Forum' started by Stuart Wright, Apr 19, 2002.

  1. Stuart Wright

    Stuart Wright
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    I had a fright the other morning when my PC wouldn't boot. I took the video card out and put it back and everything is fine, now. But it made me think about disc recovery and I'm thinking about making PC#2 (rarely used PII 233 connected to the network) a server by installing a couple of the 8mb cache 120gig Western Digital drives and a £25 raid controller to mirror the data.
    Are they any good? My network is 10/100 with a 10/100 4 port hub and 10/100 network cards connected via UTP. Will disc access from the server be quick?
    I.e. as quick as data from the local drive? HD speed is the bottleneck in my system at the moment.
    Your thoughts/advice appreciated.
     
  2. laurel

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    You can get some pretty good results with Raid. Mirrored solution is good. Obviously two drives mirrored will only give the same performance as a single drive. If you want to improve performance more, you need to look at striping as well as mirroring but this will require at least 3 drives, 4 even better. Hot-swap drive bays with server case are a good idea but obviously extra cost.

    You should get decent performance from the WD 120g anyway. performance over the lan is hard to predict. This will be effected by other factors such as how fast the server can "feed" the information over the lan, and how fast your machine (workstation) can process the incoming information. The data is not being fed directly from the system bus, but through the network card and associated network protocols. With the type of machine you are using as a server (PII 233) this would probably be the bottleneck. You would probably see an improvement by upping the spec of the server as well.

    I would say the performance will be good, but not as fast as a locally installed drive. I assume you are running at 100mbs on the lan by the way.

    Final thought is on backup solutions. Do you have any in place? I would always recommend looking at some kind of security backup - how often will depend on the amount of work you store on the system. You could look here at DAT (which is reducing in price all the time). If you can selectively backup and have a CD Writer, this can also be a good solution. After all - you can have as many hard drives you like - but if there is a fire (god forbid) you would lose them all.

    Hope this helps.

    Happy to answer any specifics.

    Cheers

    Laurel
     
  3. mjn

    mjn
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    fully experienced in RAID, 0, 1, 5 etc...what do you want know?
     
  4. Stuart Wright

    Stuart Wright
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    If I go for Raid, I would want the system to work if one of the drives fails until a replacement is installed. My primary concern is data integrity over speed. I got the spec of the server wrong - it's an AMD K6 500 with 768 meg of RAM. Which is the best raid adapter to go for. I don't have an unlimited budget !
    I would burn selected data to CD periodically though in an emergency, most of the information is online at the websites anyway.
    A friend has suggested an alternative of installing one 120 locally as my primary hard drive and using something like Norton ghost to backup to a second drive each night. That way a failure in a raid controller would not render both drives corrupt. Plus I would get the full advantage of the speed of the drive.
    Is this a better alternative?
     
  5. laurel

    laurel
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    If integrity & un-interrupted use is your main concern, then raid (mirrored) is hard to beat.

    You can pick up reasonable IDE raid controllers for about £30. Iwill do a decent one I have used. Available from CCL Computers

    There are (as always) lots of solutions to your problem, only limited by convenience and budget. The "Ghost" idea is workable, but I would suggest this would take quite a while every night to run (to ghost the whole drive).

    You could install the raid controller in your workstation, thus giving you the speed and convenience, then set up a selective backup to the server.

    As I said, various solutions are available. You need to think about exactly what you require.

    From what I can understand from your post, I would suggest mirrored raid in the server. If you can afford it - and want more speed, you can then buy 2 more drives to give you a striped/mirrored solution.

    Cheers

    Laurel
     
  6. Nic Rhodes

    Nic Rhodes
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    Spectre

    I use a RAID HCPC now, despite being told that it was over kill for HCPC here. I originally took the advice from board members and disabbled it but had a 'failure', therefore I activated the RAID facility. Personally I think it is worth the effort. I lost loads of stuff and learned a lesson.

    You have had the warning.......;)
     
  7. mjn

    mjn
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    Well RAID 1 (mirroring) is fault tolerant of a drive failure, as it uses 2 drives. Both drives contain the same data.

    However, speed is reduced, as the PC/server has to access 2 drives instead of 1.

    RAID 5 (distruted parity) is a better option, however it is more costly.

    minimum of 3 drives, but you get better read/write performance.
     
  8. laurel

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    MJN

    Not strictly true with a hardware raid controller, as this would do the mirroring for you and has it's own processor. There is no extra impact on the workstation processor.

    It would be true with software raid though.

    cheers

    Laurel
     
  9. MartinImber

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    Well we have got 2 RAID customer servers 4.11 & 5.1

    And almost all the others are Mirrored

    We have had two servers play up due to hard disk failures - since they were mirrored they just kept working, power down add a new drive, power up, auto remirror.

    So easy and so reliable, and it is also obvious.

    Demirrored one site when the drives filled up, users kept working, just the disk space doubled.

    I'd say mirroring is less hassle then RAID.

    Don't know how Windows would handle it - but mirroring is easiest on hard ware too - two identical drives
     
  10. MartinImber

    MartinImber
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    Oh mirrored servers run no slower than unmirrored
     
  11. mjn

    mjn
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    i refuse to discuss software RAID as its a joke. :)

    But RAID 1, eventhough the RAID controller has its own processor and cache, performance is still degraded.

    Read performance is the worst hit.
     
  12. mjn

    mjn
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    er....mirroring is RAID, RAID 1 to be more accurate.
     
  13. Stuart Wright

    Stuart Wright
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    Ok, thanks all. Is there a preferred RAID controller?
    Do all hardware RAID controllers continue to function seamlessly with one drive on the blink?
     
  14. laurel

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    Spectre

    If you were talking SCSI, then yes - there are some that are used in preference. IDE Raid is a fairly recent occurence, and there is not much between them. Most use the same chipset anyway. There are some recent motherboards that include IDE Raid now - these also use the same chipset.

    If you are mirroring then yes. Unfortunately unless you have a hot swap drive bay system, your gonna have to power down to change the drive though.

    Cheers

    Laurel
     
  15. Stuart Wright

    Stuart Wright
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    It has to be EIDE. I need at least 40 Gig and SCSI drives are too expensive. It's £300 + VAT for the drives as it is. Ok so £25 controller it is, then. And don't mind powering down to swap out HDD. Fingers crossed it would never happen, anyway.
    Thanks again.
     
  16. mjn

    mjn
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    u need to decide whether to go IDE or SCSI RAID.

    IDE is cheaper, but options on RAID are less, and performance isn't the best.

    SCSI is more expensive, but more RAID options, and fast performance.

    IDE controllers that support 0 (stripping), 1 (mirroring) and 0+1 aree quite cheap, around £50.

    SCSI controllers start at about £200, but support all RAID versions.

    Under RAID 1, disk performance does not reduce. But under RAID 5, disk perfermance is reduced, as 4 drives have to do the work of 5, plus fault tolerance is no more, until you replace the faulty drive.
     
  17. laurel

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    I think Spectre beat you to it there mjn :)

    For most people, the cost of SCSI is off-putting.

    With the new IDE drives I think IDE RAID is a very good cost/performance compromise, although as you correctly point out - you are limited to modes 0 & 1 or 0+1.

    Personally I'm still baffled as to why SCSI commands a much higher price. It is perhaps only due to the commercial nature of the product and the fact the manufacturers can therefore get away with it. Most organisations with large SCSI arrays will pay the price no problem.

    Cheers

    Laurel
     
  18. mjn

    mjn
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    performance = high price

    if SCSI was cheaper, nobody would buy IDE drives....

    however Adaptec have some IDE Ultra66 / 100 RAID controllers just out, which will do RAID 5, but they are very expensive, but you can't get hot-plug IDE drives, so they are a bit pointless.
     
  19. tomson

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    For general use IDE is more than fast enough in a raid setup. SCSI is great if you need the speed, say for video work using 10k RPM disks in a striped set up, but a bit of an overkill for most other duties.

    SCSI drive prices used to be pretty reasonable before high capacity/high RPM IDE drives took over - now lack of demand has forced up the price.

    Acard and Adaptec both make great controller cards.
     

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