• Tomasz Majchrzak's avatar
    raid5-ppl: PPL support for disks with write-back cache enabled · 1532d9e8
    Tomasz Majchrzak authored
    In order to provide data consistency with PPL for disks with write-back
    cache enabled all data has to be flushed to disks before next PPL
    entry. The disks to be flushed are marked in the bitmap. It's modified
    under a mutex and it's only read after PPL io unit is submitted.
    A limitation of 64 disks in the array has been introduced to keep data
    structures and implementation simple. RAID5 arrays with so many disks are
    not likely due to high risk of multiple disks failure. Such restriction
    should not be a real life limitation.
    With write-back cache disabled next PPL entry is submitted when data write
    for current one completes. Data flush defers next log submission so trigger
    it when there are no stripes for handling found.
    As PPL assures all data is flushed to disk at request completion, just
    acknowledge flush request when PPL is enabled.
    Signed-off-by: default avatarTomasz Majchrzak <tomasz.majchrzak@intel.com>
    Signed-off-by: default avatarShaohua Li <sh.li@alibaba-inc.com>
raid5-ppl.txt 2.68 KB