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RAID or Swap File move for new system?

By Flyer
Jan 7, 2006
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  1. This is a great site, been lurking for a few days now...

    I am putting together a new system and through an accident ;) I have 4 HDD, 2x300GB SATA and 2x320 GB SATA II. The idea was a 2 HDD RAID 0 setup, but now I have a question.

    What would get me the best performance:
    - RAID 0 with 2 drives
    - No RAID, but WinXP Pro swap file on the non-OS HDD
    - RAID 5 with all four HDD (this is RAID 0 with redundancy, right? How's the performance?)
    - Another option, keeping in mind speed is the goal. Does RAID 0 really give that much of a performance increase?

    Any help will be greatly appreciated...I may just send two back and get some $$ back!
     
  2. Nodsu

    Nodsu TS Rookie Posts: 9,431

    The swapfile performance depends on how much you actually use it. If you have plenty of RAM, then you could keep your swap on any slow disk and you would barely notice.

    Can you actually do RAID5 on your controller? Or is it software RAID? RAID5 is slower than 0 when writing and it is optimal when you have an odd number of drives. I wouldn't recommend it across 4 HDDs.

    If you have a kickass system that can do RAID5 then perhaps it can do RAID 1+0 - a mirror of stripes. This way you would get the speed of 0 with redundancy of 1. You'd lose half of your disk space of course.
     
  3. jobeard

    jobeard TS Ambassador Posts: 13,426   +317

    it is never recommended to place the swap drive on a raid.
    you get better performance by using a separate HD on an alternate channel.
     
  4. Nodsu

    Nodsu TS Rookie Posts: 9,431

    Why not swap on RAID? It'd be faster, no?
    And if you put it on a non-zero RAID level, you ensure that your system doesn't crash instantly in case the disk carrying the swap fails.
     
  5. jobeard

    jobeard TS Ambassador Posts: 13,426   +317

    Performance Raid stipes the files across HDs. any hd failure is catistrophic.
    Redundancy Raid Mirrors the files and thus hd failure is recovered.

    Mirroring a striped filesystem is a performance degradation.

    Classical guidelines suggest non-raid swap partitions or drives.
     
  6. Nodsu

    Nodsu TS Rookie Posts: 9,431

    Perhaps you can provide some materials that would explain these "guidelines"? urely the great classics have done extensive benchmarking and calculations to back their recommendations.

    I am very interested in RAID systems and all kinds of test results, calculations etc really help me with my work.
     
  7. jobeard

    jobeard TS Ambassador Posts: 13,426   +317

    see this article

    usually, if more than one swap partition is defined, the OS will automatically stripe the access itself. dedicating the HD to swap access only,
    avoids all i/o delays from other work and the media screams.

    user comments, swap file performace on raid sets
    see this forum

    tweakXP says this

    no one says swapping on a Raid will not work -- it's just not the best option
    if all factors are considered. remember that reliability of two devices is the product of the individual reliability numbers, eg 0.9 * 0.9 = 0.81, a reduction in reliability.
     
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