2013/4/16 Mark Kampe <[email protected]>: > RADOS is the underlying storage cluster, but the access methods (block, > object, and file) stripe their data across many RADOS objects, which > CRUSH very effectively distributes across all of the servers. A 100MB > read or write turns into dozens of parallel operations to servers all > over the cluster.
Let me try to explain. AFAIK check will split datas into chunks of 4MB each, so, a single 12MB file will be stored in 3 different chunks across multiple OSDs and then replicated many times (based on value of replica count) Let's assume a 12MB file and a 3x replica. RADOS will create 3x3 chuks for the same file stored on 9 OSDs When reading AFAIK replicas are not used, so all reads are done to the "master copy". But these 3 chunks are read in parallel on multiple OSDs or all read request are done trough a single OSD? In the first case we will have 3x bandwidth for read operations directed to a file with at least 3 chunks, in the latter we have a big bottleneck. -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
