[cc' ceph-devel] Hi Sam,
Here is how chunks are expected to be aligned: https://github.com/ceph/ceph/blob/4c4e1d0d470beba7690d1c0e39bfd1146a25f465/src/osd/ErasureCodePluginJerasure/ErasureCodeJerasure.cc#L365 unsigned alignment = k*w*packetsize*sizeof(int); if ( ((w*packetsize*sizeof(int))%LARGEST_VECTOR_WORDSIZE) ) alignment = k*w*packetsize*LARGEST_VECTOR_WORDSIZE; return alignment; If you are going to encode small objects, it may very well lead to oversized chunks if packetsize is large. At the moment the default is 3072 https://github.com/ceph/ceph/blob/4c4e1d0d470beba7690d1c0e39bfd1146a25f465/src/common/config_opts.h#L406 A value I picked when experimenting with 1MB objects encoding ( http://dachary.org/?p=2594 ). I'm not entirely sure why the alignment is calculated the way it is. Andreas certainly has a better understanding on this topic. Cheers -- Loïc Dachary, Artisan Logiciel Libre
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