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Recently upgraded my FreeBSD install to FreeBSD 9.1-stable from the 9-stable branch. I have two SATA hard drives (/dev/ada0, /dev/ada1) in a geom mirror, with nothing between : [/dev/ada0, /dev/ada1] --> /dev/mirror/gm0, which I then partition for root etc.

After upgrading from 9.0-stable to 9.1-stable, I found these messages on the console:

GEOM_MIRROR: cancelling unmapped because of ada0
GEOM_MIRROR: cancelling unmapped because of ada1
GEOM_MIRROR: Device mirror/gm0 launched (2/2).

Everything still seems to work, the mirror seems healthy and the machine works just fine, peformance is fine.

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up vote 0 down vote accepted

According to What's new to FreeBSD 10, 'unmapped vmio' buffers are coming to FreeBSD, as a performance benefit, and it would seem that the geom code in 9-stable has picked up some of the support for it.

According to commit r252010, the geom mirror provider is trying to use unmapped vmio, but can't because the ada provider for my SATA disks doesn't yet provide support for it:

/* A provider underneath us doesn't support unmapped */
if ((dp->flags & G_PF_ACCEPT_UNMAPPED) == 0) {
        G_MIRROR_DEBUG(0, "cancelling unmapped "
            "because of %s\n", dp->name);
        pp->flags &= ~G_PF_ACCEPT_UNMAPPED;

So it would seem that this error can be safely ignored, and will probably go away once universal unmapped vmio buffer support is integrated into FreeBSD

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