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    SubjectRe: Btrfs: broken file system design
    Date
    "Daniel Taylor" <Daniel.Taylor@wdc.com> writes:
    >
    > As long as no object smaller than the disk block size is ever
    > flushed to media, and all flushed objects are aligned to the disk
    > blocks, there should be no real performance hit from that.

    The question is just how large such a block needs to be.
    Traditionally some RAID controllers (and possibly some SSDs now)
    needed very large blocks upto MBs.

    >
    > Otherwise we end up with the damage for the ext[234] family, where
    > the file blocks can be aligned, but the 1K inode updates cause
    > the read-modify-write (RMW) cycles and and cost >10% performance
    > hit for creation/update of large numbers of files.

    Fixing that doesn't require a new file system layout, just some effort
    to read/write inodes in batches of multiple of them. XFS did similar
    things for a long time, I believe there were some efforts for this
    for ext4 too.

    -Andi
    --
    ak@linux.intel.com -- Speaking for myself only.


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