Monthly Archives: December 2013

Benchmarking Ceph erasure code plugins

The erasure code implementation in Ceph relies on the jerasure library. It is packaged into a plugin that is dynamically loaded by erasure coded pools. The ceph_erasure_code_benchmark is implemented to help benchmark the competing erasure code plugins implementations and to … Continue reading

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Profiling CPU usage of a ceph command (callgrind)

After compiling Ceph from sources with: ./configure –with-debug CFLAGS=’-g’ CXXFLAGS=’-g’ The crushtool test mode is used to profile the crush implementation with: valgrind –tool=callgrind \ –callgrind-out-file=crush.callgrind \ src/crushtool \ -i src/test/cli/crushtool/one-hundered-devices.crushmap \ –test –show-bad-mappings The resulting crush.callgrind file can then … Continue reading

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Profiling CPU usage of a ceph command (gperftools)

After compiling Ceph from sources with: ./configure –with-debug CFLAGS=’-g’ CXXFLAGS=’-g’ The crushtool test mode is used to profile the crush implementation with: LD_PRELOAD=/usr/lib/libprofiler.so.0 \ CPUPROFILE=crush.prof src/crushtool \ -i src/test/cli/crushtool/one-hundered-devices.crushmap \ –test –show-bad-mappings as instructed in the cpu profiler documentation. The … Continue reading

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wget on an OpenStack instance hangs ? Try lowering the MTU

Why would OpenStack instances fail to wget a URL and work perfectly on others ? For instance: $ wget -O – ‘https://ceph.com/git/?p=ceph.git;a=blob_plain;f=keys/autobuild.asc’ Connecting to ceph.com (ceph.com)|208.113.241.137|:443… connected. HTTP request sent, awaiting response… 200 OK Length: unspecified [text/plain] Saving to: `STDOUT’ … Continue reading

Posted in Havana, openstack, tinc | 1 Comment

Testing a Ceph crush map

After modifying a crush map it should be tested to check that all rules can provide the specified number of replicas. If a pool is created to use the metadata rule with seven replicas, could it fail to find enough … Continue reading

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