Btrfs Working On RAID1 Round-Robin Read Balancing

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  • microcode
    Senior Member
    • Mar 2013
    • 2378

    #31
    Originally posted by curfew View Post
    Either it is impossible because the codebase is shit, or it's just code waiting to be written. "It is complicated" is not an excuse for programmers.
    You sound like somebody who has never worked on a piece of software like this... btrfs is a filesystem, if they screw up an update millions of people are harmed. Statistically speaking, if btrfs introduces a data corruption bug to make the on-disk format suit round robin reads better, then one or more people will commit suicide from the third or fourth order consequences.

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    • waxhead
      Premium For Life
      • Jul 2014
      • 1153

      #32
      Originally posted by curfew View Post
      Either it is impossible because the codebase is shit, or it's just code waiting to be written. "It is complicated" is not an excuse for programmers.
      With this comment you only make a fool out of yourself. First you need to understand how BTRFS store data, then you need to look at the implementation. I also doubt you have done any serious programming yourself considering your last sentence there.


      http://www.dirtcellar.net

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      • Developer12
        Senior Member
        • Dec 2019
        • 1584

        #33
        Originally posted by Britoid View Post

        RAID in BTRFS also works very differently to standard raid. The disks are not identical, you can't just read the same location on a second drive.
        Same with ZFS, but somehow they didn't screw this up. Multiplexing based on a process' PID has got to be one of the most hacky bandaid solutions I've ever heard of. Not only do you now introduce a weird dependency on a userspace property (oops, two processes randomly have similar PIDs and both try to always read from the same disk, killing performance) but you also kill your performance in cases with massive single-process consumers like, say, databases. Pretty important use case. Should have just done it right the first time.

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        • S.Pam
          Senior Member
          • Oct 2018
          • 687

          #34
          Originally posted by bezirg View Post

          How can RAID1 give you same disk space as RAID10?
          You can read about the supported Profiles ("RAID" modes) here https://wiki.tnonline.net/w/Btrfs/Pr...files_Overview

          For example RAID1c4 has 4 copies of the data and can survive 3 broken disks.

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          • elml
            Junior Member
            • Jun 2017
            • 11

            #35
            Originally posted by phoronix View Post
            Phoronix: Btrfs Working On RAID1 Round-Robin Read Balancing

            ... RAID1 round-robin read balancing...

            https://www.phoronix.com/news/Btrfs-...d-Robin-Coming
            Hallelujah!

            The old trick of selection of "which mirrored disk" by "modulo PID" completely ignored the loading on whichever disk...

            That old selection by PID may well be fine for a blizzard of small reads for Twits... Too often it was hopeless for media work where one single disk in a cluster would too often suffer a pile-up...

            So, this new scheme should undo the need for raid10...

            Meanwhile, whatever happened to the patches that were submitted that actually did try to do load balancing?...


            Be excellent to one another!
            Martin
            Last edited by elml; 18 December 2024, 08:11 PM.

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