Friday, November 28, 2014

Ceph: recover OSDs after SSD journal failure [feedly]

Ceph: recover OSDs after SSD journal failure
// Ceph

A common recommendation is to store OSD journal on a SSD drive which implies loosing your OSD if this journal fails. This article assumes that your OSDs have been originally deployed with ceph-disk. You will also realise that it's really simple to bring your OSDs back to life after replacing your faulty SSD with a new one.

Even if OSDs have segfaulted, data directories are still mounted so you can easily get the journal FSID:

bash $ journal_uuid=$(sudo cat /var/lib/ceph/osd/ceph-0/journal_uuid) $ sudo sgdisk --new=1:0:+20480M --change-name=1:'ceph journal' --partition-guid=1:$journal_uuid --typecode=1:$journal_uuid --mbrtogpt -- /dev/sdk

The journal symlink should not be broken anymore and available at /var/lib/ceph/osd/ceph-0/journal. Now we recreate the journal on our new partition and start our OSD.

bash $ sudo ceph-osd --mkjournal -i 20 $ sudo service ceph start osd.20

Simple right? To create more partitions, simply change the 1 in the sgdisk command with another number which represents the partition number.


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