lkml.org 
[lkml]   [2019]   [Jun]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 09/19] btrfs: limit super block locations in HMZONED mode
    On Fri, Jun 07, 2019 at 10:10:15PM +0900, Naohiro Aota wrote:
    > When in HMZONED mode, make sure that device super blocks are located in
    > randomly writable zones of zoned block devices. That is, do not write super
    > blocks in sequential write required zones of host-managed zoned block
    > devices as update would not be possible.

    This could be explained in more detail. My understanding is that the 1st
    and 2nd copy superblocks is skipped at write time but the zone
    containing the superblocks is not excluded from allocations. Ie. regular
    data can appear in place where the superblocks would exist on
    non-hmzoned filesystem. Is that correct?

    The other option is to completely exclude the zone that contains the
    superblock copies.

    primary sb 64K
    1st copy 64M
    2nd copy 256G

    Depends on the drives, but I think the size of the random write zone
    will very often cover primary and 1st copy. So there's at least some
    backup copy.

    The 2nd copy will be in the sequential-only zone, so the whole zone
    needs to be excluded in exclude_super_stripes. But it's not, so this
    means data can go there. I think the zone should be left empty.

    \
     
     \ /
      Last update: 2019-06-18 00:53    [W:4.031 / U:0.016 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site