2017-11-16 14:05 GMT+01:00 Georgios Dimitrakakis <giorgis@xxxxxxxxxxxx>:
Dear cephers,
I have an emergency on a rather small ceph cluster.
My cluster consists of 2 OSD nodes with 10 disks x4TB each and 3 monitor nodes.
The version of ceph running is Firefly v.0.80.9 (b5a67f0e1d15385bc0d60a6da6e7fc810bde6047)
The cluster originally was build with "Replicated size=2" and "Min size=1" with the attached crush map,
which in my understanding this replicates data across hosts.
The emergency comes from the violation of the golden rule: "Never use 2 replicas on a production cluster"
Unfortunately the customers never really understood well the risk and now that one disk is down I am in the middle and I must do everything in my power not to loose any data, thus I am requesting your assistance.
Here is the output of
$ ceph osd tree
# id weight type name up/down reweight
-1 72.6 root default
-2 36.3 host store1
0 3.63 osd.0 down 0 ---> DISK DOWN
1 3.63 osd.1 up 1
2 3.63 osd.2 up 1
3 3.63 osd.3 up 1
4 3.63 osd.4 up 1
5 3.63 osd.5 up 1
6 3.63 osd.6 up 1
7 3.63 osd.7 up 1
8 3.63 osd.8 up 1
9 3.63 osd.9 up 1
-3 36.3 host store2
10 3.63 osd.10 up 1
11 3.63 osd.11 up 1
12 3.63 osd.12 up 1
13 3.63 osd.13 up 1
14 3.63 osd.14 up 1
15 3.63 osd.15 up 1
16 3.63 osd.16 up 1
17 3.63 osd.17 up 1
18 3.63 osd.18 up 1
19 3.63 osd.19 up 1
and here is the status of the cluster
# ceph health
HEALTH_WARN 497 pgs degraded; 549 pgs stuck unclean; recovery 51916/2552684 objects degraded (2.034%)
Althoug OSD.0 is shown as mounted it cannot be started (probably failed disk controller problem)
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 251G 4.1G 235G 2% /
tmpfs 24G 0 24G 0% /dev/shm
/dev/sda1 239M 100M 127M 44% /boot
/dev/sdj1 3.7T 223G 3.5T 6% /var/lib/ceph/osd/ceph-8
/dev/sdh1 3.7T 205G 3.5T 6% /var/lib/ceph/osd/ceph-6
/dev/sdg1 3.7T 199G 3.5T 6% /var/lib/ceph/osd/ceph-5
/dev/sde1 3.7T 180G 3.5T 5% /var/lib/ceph/osd/ceph-3
/dev/sdi1 3.7T 187G 3.5T 6% /var/lib/ceph/osd/ceph-7
/dev/sdf1 3.7T 193G 3.5T 6% /var/lib/ceph/osd/ceph-4
/dev/sdd1 3.7T 212G 3.5T 6% /var/lib/ceph/osd/ceph-2
/dev/sdk1 3.7T 210G 3.5T 6% /var/lib/ceph/osd/ceph-9
/dev/sdb1 3.7T 164G 3.5T 5% /var/lib/ceph/osd/ceph-0 ---> This is the problematic OSD
/dev/sdc1 3.7T 183G 3.5T 5% /var/lib/ceph/osd/ceph-1
# service ceph start osd.0
find: `/var/lib/ceph/osd/ceph-0': Input/output error
/etc/init.d/ceph: osd.0 not found (/etc/ceph/ceph.conf defines mon.store1 osd.6 osd.9 osd.1 osd.4 osd.3 osd.2 osd.8 osd.5 osd.7 mds.store1 mon.store3, /var/lib/ceph defines mon.store1 osd.6 osd.9 osd.1 osd.4 osd.3 osd.2 osd.8 osd.5 osd.7 mds.store1)
I have found this: http://ceph.com/geen-categorie/admin-guide-replacing-a- failed-disk-in-a-ceph-cluster/
and I am looking for your guidance in order to properly perform all actions in order not to loose any data and keep the ones of the second copy.
What guidance are you looking for besides the steps to replace a failed disk (which you already found) ?
If i look at your situation, there is nothing 'down' in terms of availability of pgs, just a failed drive which needs to be replaced.
Is the cluster still recovering? It should reach HEALTH_OK again after rebalancing the cluster when an OSD goes down.
If it stopped recovering it might have to do with the ceph 'tunables' which are not set to optimal by default on firefly and that prevents further rebalancing.
WARNING: Don't just set tunables to optimal because it will trigger a massive rebalance!
Perhaps the second golden rule is to never run a CEPH production cluster without knowing (and testing) how to replace a failed drive. (I'm not trying to be harsh here).
Kind regards,
Caspar
Best regards,
G.
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