RAID 5 slow write speeds

  • Hi everybody,


    I'm currently experiencing some heavy problems with my RAID 5 BTRFS.


    Background:


    I started with a ext4 RAID 1 (2 disks, 3TB)
    One week ago I added one more disk and converted to RAID 5 (with some problems during conversion, but solved)


    After that, I converted the ext4 file system to BTRFS and removed conversion snapshot.



    Now the write speed of the RAID 5 is REALLY slow - even below 10 MB/s.
    CPU load seems to be ok (about 20%).


    dbench shows only ~0.01 MB/s:



    mdstat:



    Bash
    [bbsan@omvserver volume1]$ cat /proc/mdstat
    Personalities : [raid6] [raid5] [raid4]
    md127 : active raid5 sdb[0] sda[3] sdc[2]
          5860270080 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
    
    
    unused devices: <none>


    Any suggestions?

    • Offizieller Beitrag

    Any suggestions?

    Don't use btrfs raid 5. That is very unstable right now.

    omv 7.0.4-2 sandworm | 64 bit | 6.5 proxmox kernel

    plugins :: omvextrasorg 7.0 | kvm 7.0.10 | compose 7.1.2 | k8s 7.0-6 | cputemp 7.0 | mergerfs 7.0.3


    omv-extras.org plugins source code and issue tracker - github


    Please try ctrl-shift-R and read this before posting a question.

    Please put your OMV system details in your signature.
    Please don't PM for support... Too many PMs!

    • Offizieller Beitrag

    That wasn't clear from reading the first half of your post. What kind of hardware is this on? Are you using the backports kernel?

    omv 7.0.4-2 sandworm | 64 bit | 6.5 proxmox kernel

    plugins :: omvextrasorg 7.0 | kvm 7.0.10 | compose 7.1.2 | k8s 7.0-6 | cputemp 7.0 | mergerfs 7.0.3


    omv-extras.org plugins source code and issue tracker - github


    Please try ctrl-shift-R and read this before posting a question.

    Please put your OMV system details in your signature.
    Please don't PM for support... Too many PMs!

  • The behavior occured with normal and backports kernel on OMV3.
    However, I solved it by recreating the complete RAID and FS. Took some time, now everything works as expected.

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