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Thread: BTRFS much slower than ext4?

  1. #1
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    Default BTRFS much slower than ext4?

    I recently tried out BTRFS on my new 1.5 terrabyte hard drive, using ext3 as /boot. I also have 3 gigabytes of swap. Anyway, I've found that the new Kubuntu 10.10 installation on this BTRFS hard drive has much worse performance than my old ext4 hard drive. Also, it doesn't take much with the new installation for the CPU to be so overwhelmed that my entire computer becomes unresponsive for a bit. One theory that I have is that BTRFS uses a lot more RAM than ext4 because I only have 1 gigabyte of RAM in my computer. Does anyone know anything about this?

  2. #2
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    When an OS slows down, it could be caused by a few things. I tend to think BTRFS isn't one of them. More likely is CPU being drained by misconfigured video driver, the silly search tools that became a fashion for a while and were used by Ubuntu, or other tools like "locate" being run by the OS (automatically) every day. Imho 1GB ram is plenty for modern Linux kernels.

    When you get slowdown, run "top" from the command line and have a look what is happening.

  3. #3
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    I've already done that. There's nothing in particular that's causing the slowdown. Programs that previously hadn't used as much CPU, now seem to be using more. A misconfigured video driver might be the problem. I'm using NVIDIA's blob. The only change in how I've set up my video driver is that I set my image settings to "High Performance" instead of something in the middle. I also set both antialiasing and anisotropic filtering settings to "Use Application Settings" instead of "Enhance Application Settings" and then giving them the max setting. Any thoughts?

  4. #4
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    Is BTRFS 4k-sector aware?

  5. #5
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    btrfs within the Linux 2.6.35 kernel (that Kubuntu 10.10 uses) has known serious performance issues. Those have been fixed in newer kernels. Try .38rc4 and it will fly.

  6. #6
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    That's great news. I can't wait until Kubuntu 11.04 when my drive will speed up. Also, I look forward to seeing BTRFS performance metrics comparing 10.10 to 11.04 and comparing it to ext4.

  7. #7
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    Quote Originally Posted by Prescience500 View Post
    That's great news. I can't wait until Kubuntu 11.04 when my drive will speed up. Also, I look forward to seeing BTRFS performance metrics comparing 10.10 to 11.04 and comparing it to ext4.
    It should work with a simple distribution upgrade, but sometimes filesystems change so much that it is recommended to reformat the partition. Not sure if that is the case here, though, don't think so actually.

  8. #8
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    Btrfs has no good fsck tool yet and wins only in threaded IO. I would not use it in production yet.

  9. #9
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    I know it's not ready. I'm only using it on my home computer. I don't have anything critical on it that isn't backed up. Speaking of which, what's the word on the progress of fsck tools? Is there any word on when they will be ready?

  10. #10
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    According to recent performance metrics, BTRFS doesn't seem much faster (except for just a few metrics), even with the latest snapshot of kernel 2.6.38.

    http://openbenchmarking.org/result/1...IV-1102232IV10

    Maybe it'll be different once things like compression and what not are added.

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