btrfs (and zfs) slow?

  • Hi
    I'm using btrfs on a dedicated drive holding lxd containers, and I am today thinking to also migrate my data and backup drives from ext4 to btrfs.
    Yet, I read several benchmarks notably those of phoronix.com (
    https://www.phoronix.com/scan.…item=linux-50-filesystems or https://www.phoronix.com/scan.…cle&item=linux55-ssd-raid ) saying that btrfs and zfs were noticeably slower and something very slower than ext4.


    What's your thoughts about it? Have anyone compared between ext4 and btrfs or zfs on the speed level, notably for shared drive access and backups?
    (I know btfs and zfs offer plenty of extra features compared to ext4, I mainly wonder if there is a significant performance cost to use them versus the plain old ext4)

    • Offizieller Beitrag

    I'm running ZFS on two servers and ext4 on two other boxes. For my purposes, while ext4 "seems" to be a bit faster, ZFS copies and moves are not that much slower.


    From a practical standpoint:
    Any filesystem type, on most hardware platforms, is fast enough to stream media files and handle concurrent LAN user requests in a home environment. The difference in speed between BTRFS or ZFS and EXT4 might be noticeable with massive files copies, moves between drives, large rsync transfer operations, and that kind of thing. On the other hand, I generally don't sit with the server and watch large file transfers. I set it up and leave, or automate something like rsycn replication to kick off after-hours.


    Essentially, I've never stressed my servers in such a way to where I feel that I need that bit of extra speed EXT4 provides. In my scenario, the difference is not noticeable.

  • Keep in mind those are specific stress tests. They are looking for limits.


    I've used the car analogy many times. Car A has a top speed of 250mph. Car B, 240. Car C 180.


    The vast majority of the time and and vast majority of people will never hit those limits. They will never see a performance difference because they aren't running simulated workloads back to back and graphing the results.


    It's not an exact comparison; it's easier to hit limitations on computer hardware than a super fast car. But it helps to bring the thoughts out.


    I've been using btrfs for years under many different hardware and software setups. It's never been a concern of speed for me. Btrfs has always performed great, usually if I'm hitting some limit it's not because of btrfs.


    That said, btrfs has many more modern features that really should make it the default filesystem used for most systems.

    • Offizieller Beitrag

    That said, btrfs has many more modern features that really should make it the default filesystem used for most systems.

    I'd agree but,, I had a couple problems a few years ago when testing it. I lost the entire contents of an external 4TB drive twice. It was a rough test, in a mobile application, where power can be expected to be abruptly removed. (This was one of the reasons for selecting BTRFS, for COW.) Interestingly, I started testing again on the exact same hardware and now it's working fine.


    While I know patches are being applied (else I'd have lost the 4TB drive again), the project's status seems to have been frozen for years.

  • That status page isn't the best, granted.


    However, many people have tried to get failures with raid56 and have not. It just works.


    I've been using single drive, RAID1 and RAID10 for many years and it's never has any issues.

    • Offizieller Beitrag

    Unfortunately, anecdotal experiences, both mine (bad in times past - good lately) and yours (always good) are not enough to base project decisions on.


    While I don't make the decisions on what is, or is not, supported in OMV's GUI:
    If only one in 250 OMV users had a BTRFS problem, the resultant wave of support requests on this forum would be considerable. (There are thousands of downloads per week.) That's the problem with adopting anything new - not knowing what to expect. And interestingly, while BTRFS is getting some age on it, one would think it's still a new project with the number of issues still outstanding.

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