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I think that for most desktop purposes RAID0 is useless. Gamers like to THINK that they're getting some performance benefit from RAID0--until someone actually bothers to measure it. RAID1, OTOH, ...
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  1. #11
    Linux User IsaacKuo's Avatar
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    I think that for most desktop purposes RAID0 is useless. Gamers like to THINK that they're getting some performance benefit from RAID0--until someone actually bothers to measure it.

    RAID1, OTOH, can be nice for your OS and maybe some of your frequently updated data files. You can get a real performance boost out of it with reduced seek times and multiple simultaneous file reads (like reading web pages with a lot of cached files).

    RAID5 is mainly useful for when you want a huge amount of storage space but don't want it split up into a bunch of smaller volumes. The cost of a single 500gig drive is high, compared to the cost of several 200gig drives. You could theoretically use "JBOD" or LVM or RAID0 to string together a bunch of drives into one big volume, but these lack redundancy so a single drive failure means you lose all your data. RAID5 has enough redundancy so that a single drive failure causes no data loss.
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  2. #12
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    RAID 0 isn't useless, though I doubt it gives 'gamers' much of performance gain. I use RAID 5 on my server simply because once I get NFS setup, all my stuff's going on there. and If one fails, the other one will start up with all the data. very very nice.

  3. #13
    Linux Engineer LondoJowo's Avatar
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    RAID1, OTOH, can be nice for your OS and maybe some of your frequently updated data files. You can get a real performance boost out of it with reduced seek times and multiple simultaneous file reads (like reading web pages with a lot of cached files).
    You just described Raid 0.

    Raid 1 is mirrored array and actually runs slower than a single drive as it takes time to synchronize the drives.

    I think that for most desktop purposes RAID0 is useless. Gamers like to THINK that they're getting some performance benefit from RAID0--until someone actually bothers to measure it.
    You will notice an overall gain in the speed that the computer/games load when running a Raid 0 array. Look at my previous post showing the performance data for single drive, 2 drive array, and 4 drive array.
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  4. #14
    Linux Engineer LondoJowo's Avatar
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    Here's some benchmarking, this is for IDE (ATA) Raid.
    http://www.dalantech.com/ubbthreads/...0/page/0#31868

    Here's the goods on SCSI.
    http://www.dalantech.com/ubbthreads/...0/page/0#31894
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  5. #15
    Linux User IsaacKuo's Avatar
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    Quote Originally Posted by LondoJowo
    RAID1, OTOH, can be nice for your OS and maybe some of your frequently updated data files. You can get a real performance boost out of it with reduced seek times and multiple simultaneous file reads (like reading web pages with a lot of cached files).
    You just described Raid 0.
    No. RAID0 does nothing to help seek times. In fact, seek times can be slower since all drive heads must seek to the same point to read data. RAID0 does little to help multiple simultaneous file reads. It still has to seek (all drives) to the first file, read it, then seek to the second file, and then read it.

    In contrast, RAID1 can help seek times and can handle multiple simultaneous file reads efficiently. When a single file is requested, the drive which has the nearest head is used. The average seek time is reduced for the same reason multiple elevators reduce wait time. When multiple files are requested, each new read request goes to a free drive (if available).

    For most of the things that you actually do on a computer, seek times are more important than sustained data transfer rate.

    Quote Originally Posted by LondoJowo
    Raid 1 is mirrored array and actually runs slower than a single drive as it takes time to synchronize the drives.
    It takes zero time to "synchronize" the drives. The drives aren't synchronized at all, except in the case of replacing a failed drive (or adding a new drive to an array).

    Instead, the way RAID1 works is that writes are performed in parallel to all drives in the array. This means that writes essentially have the same performance as the slowest drive, unless multiple drives are sharing the same IDE channel (this is a bad idea in any case). There is a neglible amount of extra time consumed sending the data to multiple drives rather than just one when the drives are on separate channels (as they should be).

    Quote Originally Posted by LondoJowo
    You will notice an overall gain in the speed that the computer/games load when running a Raid 0 array. Look at my previous post showing the performance data for single drive, 2 drive array, and 4 drive array.
    The performance data you give relates to transfer rates, which honestly aren't very important compared to seek rates for most things.

    For computer games, load times might be slightly reduced, but the overwhelming bulk of computer game data is compressed and CPU time overwhelms file loading times (even with just a single drive). Maybe if computer game publishers decide to optimize their games for people with huge superfast RAID0 arrays, then there could be a significant performance benefit. I doubt it, though, since it would boost disk consumption maybe 24fold (based on about 1bit per pixel with JPEG compression).
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  6. #16
    Linux User IsaacKuo's Avatar
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    Oh--if you don't believe me about CPU time vs disk transfer time, ask yourself why your CPU usage spikes whenever you load a game (or any other large program). It's NOT because the CPU is just sitting there waiting for the files to finish loading.
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  7. #17
    Linux Engineer LondoJowo's Avatar
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    Please explain why I can install WindowsXP in 15 minutes on a Raid 0 array versus 30 minutes on single drive or Raid 1 array.

    Any disk extensive program will benefit more from a Raid 0 array, the only drawback is no fault tolerance.
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  8. #18
    Linux User IsaacKuo's Avatar
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    Quote Originally Posted by LondoJowo
    Please explain why I can install WindowsXP in 15 minutes on a Raid 0 array versus 30 minutes on single drive or Raid 1 array.
    Because the WindowsXP install is entirely limited by sustained transfer speeds, copying files. It uses almost no CPU processing whatsoever (why would it?).

    So what? It's not something you're going to be doing every day...well, if you use a big enough RAID0 array of Maxtors, then maybe it is something you're going to be doing every day...

    For the example given (running games) or any of the more common computing tasks a typical user does most of the time, sustained transfer speeds are not very important.

    [Edit: added:]...except for Photoshop/The GIMP. Putting the page file in a RAID0 honestly does help with Photoshop or the GIMP. A lot!
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  9. #19
    Linux Engineer LondoJowo's Avatar
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    Raid 0 makes a huge difference when capturing and encoding video, not to mention having 2GB of ram also is helpful on the encoding side as well. I agree having the scratch folder on the Raid 0 for photo/graphic editing is great too but I would never place the swap(page) file on the array as it would cause major problems if the array failed.
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  10. #20
    Linux Guru techieMoe's Avatar
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    Wow. I had no idea I'd start a debate. Thank you both for keeping it about facts rather than resorting to flames.

    So from what I've read from both sides, what I do every day (run games, surf the net, develop software), RAID isn't useful. However if my everyday tasks included something like capturing video or working with high-volume multimedia it would. Does that about sum it up?
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