<p>I have setup <code>RookIO 1.4</code> cluster in Kubernetes 1.18.  with 3 nodes allocated 1TB storage on each of them.
after creating cluster. when I run the <code>ceph status</code> cluster status shows as <code>HEALTH_WARN</code> with <code>mon c is low on available space</code>.</p>
<p>There is no data stored yet. why status how low on available space? How to clear this error?</p>
<pre><code>[root@rook-ceph-tools-6bdcd78654-sfjvl /]#  ceph  status
  cluster:
    id:     ad42764d-aa28-4da5-a828-2d87205aff08
    health: HEALTH_WARN
            mon c is low on available space

  services:
    mon: 3 daemons, quorum a,b,c (age 37m)
    mgr: a(active, since 36m)
    osd: 3 osds: 3 up (since 37m), 3 in (since 37m)

  data:
    pools:   1 pools, 1 pgs
    objects: 0 objects, 0 B
    usage:   3.0 GiB used, 3.6 TiB / 3.6 TiB avail
    pgs:     1 active+clean
</code></pre>
<p>All three node has same size storage:</p>
<pre><code>sdb                                                                                                    8:16   0  1.2T  0 disk
└─ceph--a6cd601d--7584--4b1f--bf82--48c95437f351-osd--data--ae1bc856--8ded--4b1e--8c87--30ca0f0959a3 253:3    0  1.2T  0 lvm
sdb                                                                                                    8:16   0  1.2T  0 disk
└─ceph--ccaf7144--d6a0--441c--bcd5--6a09d056bd7a-osd--data--36a9b28c--7207--400a--936b--edfb3255ce0b 253:3    0  1.2T  0 lvm
sdb                                                                                                    8:16   0  1.2T  0 disk
└─ceph--53e9b8a9--8925--4b21--a6ea--f8e17a322d5c-osd--data--6b1e779c--a18a--4e4d--960e--73ca9473d02f 253:3    0  1.2T  0 lvm
</code></pre>
<p>Thanks
SR</p>

<p>This alert is for your monitor disk space that is stored normally in <code>/var/lib/ceph/mon</code>. This path is stored in root fs that isn't related to your OSDs block device. This warn is raised when this path has less than 30% available space (see <code>mon_data_avail_warn</code> which is 30 by default).
You can change it to ignore alert or resize that path to have more space for its RocksDB data.</p>
