Author Archives: Loic Dachary

What cinder volume is missing an RBD object ?

Although it is extremely unlikely to loose an object stored in Ceph, it is not impossible. When it happens to a Cinder volume based on RBD, knowing which has an object missing will help with disaster recovery.

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Tell teuthology to use a local ceph-qa-suite directory

By default teuthology will clone the ceph-qa-suite repository and use the tasks it contains. If tasks have been modified localy, teuthology can be instructed to use a local directory by inserting something like: suite_path: /home/loic/software/ceph/ceph-qa-suite in the teuthology job yaml … Continue reading

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Temporarily disable Ceph scrubbing to resolve high IO load

In a Ceph cluster with low bandwidth, the root disk of an OpenStack instance became extremely slow during days. When an OSD is scrubbing a placement group, it has a significant impact on performances and this is expected, for a … Continue reading

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Global shortcuts for emacs org-mode on Ubuntu

Let say F7 is bound, in emacs, to the org-clock-out function of Org Mode as a shortcut to quickly stop the current clock accumulating the time spent on a given task. (global-set-key (kbd “<f7>”) ‘org-clock-out) F7 can be sent to … Continue reading

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Ceph disaster recovery scenario

A datacenter containing three hosts of a non profit Ceph and OpenStack cluster suddenly lost connectivity and it could not be restored within 24h. The corresponding OSDs were marked out manually. The Ceph pool dedicated to this datacenter became unavailable … Continue reading

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puppet-ceph update

End of last year, a new puppet-ceph module was bootstrapped with the ambitious goal to re-unite the dozens of individual efforts. I’m very happy with what we’ve accomplished. We are making progress although our community is mixed, but more importantly, … Continue reading

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Ceph erasure code jerasure plugin benchmarks (Highbank ARMv7)

The benchmark described for Intel Xeon is run with a Highbank ARMv7 Processor rev 0 (v7l) processor (the maker of the processor was Calxeda ), using the same codebase: The encoding speed is ~450MB/s for K=2,M=1 (i.e. a RAID5 equivalent) … Continue reading

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workaround DNSError when running teuthology-suite

Note: this is only useful for people with access to the Ceph lab. When running a Ceph integration tests using teuthology, it may fail because of a DNS resolution problem with: $ ./virtualenv/bin/teuthology-suite –base ~/software/ceph/ceph-qa-suite \ –suite upgrade/firefly-x \ –ceph … Continue reading

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Locally repairable codes and implied parity

When a Ceph OSD is lost in an erasure coded pool, it can be recovered using the others. For instance if OSD X3 was lost, OSDs X1, X2, X4 to X10 and P1 to P4 are retrieved by the primary … Continue reading

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Ceph erasure code jerasure plugin benchmarks

On a Intel(R) Xeon(R) CPU E5-2630 0 @ 2.30GHz processor (and all SIMD capable Intel processors) the Reed Solomon Vandermonde technique of the jerasure plugin, which is the default in Ceph Firefly, performs better. The chart is for decoding erasure … Continue reading

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