Reboots under 6.0 while exercising md device

Brooks Davis brooks at
Wed Dec 21 20:35:20 PST 2005

On Wed, Dec 21, 2005 at 07:50:49PM -0800, James Long wrote:
> For some reason, this script:
> #!/bin/sh
> DEV=$(md_config -a -t malloc -s 500m)
> newfs -i 512 -U /dev/$DEV
> mount /dev/$DEV /mnt
> cp -Rp /usr/src /mnt/
> will kill my machine.  I get zillions (well, hundreds at
> least, without a serial console I can't count them)
> of:
> Dec 21 19:16:27 test kernel: g_vfs_done():md0[WRITE(offset=352649216, length=16384)]error = 28
> Dec 21 19:16:27 test kernel: g_vfs_done():md0[WRITE(offset=352665600, length=12288)]error = 28
> with varying offsets and lengths, but seemingly always error 28
> The system does not panic orderly, but rather spontaneously reboots after
> spewing a lot of the above error messages (5-20 secs worth).
> This is on a Compaq Proliant ML370 with 1 GB RAM, dmesg below.
> What do I need to fix to be able to use a RAM-backed filesystem?

From mdconfig(8):

     -t type
             Select the type of the memory disk.

             malloc   Storage for this type of memory disk is allocated with
                      malloc(9).  This limits the size to the malloc bucket
                      limit in the kernel.  If the -o reserve option is not
                      set, creating and filling a large malloc-backed memory
                      disk is a very easy way to panic a system.

As a rule, swap or vnode backed md devices are a better idea than malloc

-- Brooks

Any statement of the form "X is the one, true Y" is FALSE.
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