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Hi Vincent, There is no buffering until the object reaches 8MB. When the object is written, it has a given size. RADOS just splits the object in K chunks, padding occurs if the object size is not a
multiple of K. See also:
http://docs.ceph.com/docs/master/dev/osd_internals/erasure_coding/developer_notes/ Cheers, Maxime From:
ceph-users <ceph-users-bounces@xxxxxxxxxxxxxx> on behalf of Vincent Godin <vince.mlist@xxxxxxxxx> When we use a replicated pool of size 3 for example, each data, a block of 4MB is written on one PG which is distributed on 3 hosts (by default). The osd holding the primary will copy the block to OSDs holding
the secondary and third PG. With erasure code, let's take a raid5 schema like k=2 and m=1. Does Ceph buffer the data till it reach a amount of 8 MB which it can then divide into two blocks of 4MB and a parity control of 4MB ? Does it
just divide the data in two chunks whatever the size ? Will it use then PG1 on OSD.A to store the first block, PG1 on OSD.X to store the second block of data and PG1 on OSD.z to store the parity ?
Thanks for your explanation because i didn't found any clear explanation on how data chunk and parity
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