On Thu, 23 Sep 2010 20:43:44 +0100
Robin Doherty [off-list ref] wrote:

So maybe this is a file system problem rather than an mdadm problem?

mkfs.ext3 says:

       -m reserved-blocks-percentage
              Specify the percentage of the filesystem blocks reserved for the
              super-user.   This  avoids  fragmentation, and allows root-owned
              daemons, such as syslogd(8), to continue to  function  correctly
              after non-privileged processes are prevented from writing to the
              filesystem.  The default percentage is 5%.

this can be changed on an existing FS using tune2fs.

Also, this is not related to mdadm at all.

-- 
With respect,
Roman