[lkml]   [2008]   [Feb]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: device mapper not reporting no-barrier-support?
    On Mon, 25 Feb 2008 14:26:15 +0100 Anders Henke <> wrote:

    > Hi,
    > I'm currently stuck between Kernel LVM and DRBD, as I'm using Kernel
    > with DRBD 8.2.5 on top of an LVM2 device (LV).
    > -LVM2/device mapper doesn't support write barriers
    > -DRBD uses blkdev_issue_flush() to flush its metadata to disk.
    > On a no-barrier-device, DRBD should receive EOPNOTSUPP, but
    > it really does receive an EIO. Promptly, DRBD gives the
    > error message "drbd0: local disk flush failed with status -5".
    > The physical disk (in LVM speak) is a RAID1 on a 3ware 9650SE-2LP
    > controller; the driver 3w-9xxx supports barriers and after moving my D
    > RBD device from the LV to a single partition on the same RAID1, the
    > error messages from DRBD vanished.
    > I've posted a lengty summary of my findings to
    > ... where Lars Ellenberg from DRBD basically responded in
    > ... that DRBD does catch the EOPNOTSUPP for blkdev_issue_flush and
    > BIO_RW_BARRIER, but the lvm implementation of blkdev_issue_flush in
    > aparently does return EIO for blkdev_issue_flush.
    > So simply the question: how should a top-layer driver check wether a lower
    > device does support barriers? md-raid does check this way differently than
    > e.g. XFS does, while DRBD also adds a third way to check this.
    > Or is this "merely" a bug in drivers/md/dm.c?

    (cc dm-devel)

    I'd say it's a DM bug. Probably a hard-to-fix one though.

     \ /
      Last update: 2008-02-26 00:25    [W:0.021 / U:56.884 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site