if your cache-mode is write-back, which will cache the read object in cache tier. you can try the read-proxy mode, which will not cache the object. the read request send to primary OSD, and the primary osd collect the shards from base tier(in you case, is erasure code pool), you need to read at least k chunks to decode the object. In current code, cache tier only store the whole object, not the shards. 2016-03-31 6:10 GMT+08:00 Yu Xiang <hellomorning@xxxxxxxxxxxxx>: > Dear List, > I am exploring in ceph caching tier recently, considering a cache-tier > (replicated) and a back storage-tier (erasure-coded), so chunks are stored > in the OSDs in the erasure-coded storage tier, when a file has been > requested to read, usually, all chunks in the storage tier would be copied > to the cache tier, replicated, and stored in the OSDs in caching pool, but i > was wondering would it be possible that if only partial chunks of the > requested file be copied to cache? or it has to be a complete file? for > example, a file using (7,4) erasure code (4 original chunks, 3 encoded > chunks), when read it might be 4 required chunks are copied to cache, and i > was wondering if it's possible to copy only 2 out of 4 required chunks to > cache, and the users getting the other 2 chunks elsewhere (or assuming the > client already has 2 chunks, they only need another 2 from ceph)? can the > cache store partial chunks of a file? > > Thanks in advance for any help! > > Best, > Yu > > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > -- thanks huangjun _______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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