Ceph is a large scale storage system. You're hoping that it is going to care about and split files that are 9 bytes in size. Do this same test with a 4MB file and see how it splits up the content of the file.
On Tue, Jun 20, 2017, 6:48 AM Jonas Jaszkowic <[email protected]> wrote: > I am currently evaluating erasure coding in Ceph. I wanted to know where > my data and coding chunks are located, so I > followed the example at > http://docs.ceph.com/docs/master/rados/operations/erasure-code/#creating-a-sample-erasure-coded-pool > > and setup an erasure coded pool with k=3 data chunks and m=2 coding > chunks. I stored an object named 'NYAN‘ with content > ‚ABCDEFGHI‘ in the pool. > > The output of ceph osd map ecpool NYAN is following, which seems correct: > > osdmap e97 pool 'ecpool' (6) object 'NYAN' -> pg 6.bf243b9 (6.39) -> up > ([3,1,0,2,4], p3) acting ([3,1,0,2,4], p3) > > But when I have a look at the chunks stored on the corresponding OSDs, I > see three chunks containing the *whole *content of the original file > (padded with zeros to a size of 4.0K) > and two chunks containing nothing but zeros. I do not understand this > behavior. According to the link above: "The NYAN object will be divided in > three (K=3) and two additional chunks will be created (M=2).“, but what I > experience is that the file is replicated three times *in its whole *and > what appears to be the coding chunks (i.e. holding parity information) are > objects containing *nothing but zeros*? Am I doing something wrong here? > > Any help is appreciated! > > Attached is the output on each OSD node with the path to the chunk and its > content as hexdump: > > osd.0 > path: > /var/lib/ceph/osd/ceph-0/current/6.39s2_head/NYAN__head_0BF243B9__6_ffffffffffffffff_2 > md5sum: 1666ba51af756693678da9efc443ef44 > > /var/lib/ceph/osd/ceph-0/current/6.39s2_head/NYAN__head_0BF243B9__6_ffffffffffffffff_2 > filesize: 4.0K > /var/lib/ceph/osd/ceph-0/current/6.39s2_head/NYAN__head_0BF243B9__6_ffffffffffffffff_2 > hexdump: 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > * > 00000560 > > osd.1 > path: > /var/lib/ceph/osd/ceph-1/current/6.39s1_head/NYAN__head_0BF243B9__6_ffffffffffffffff_1 > md5sum: 1666ba51af756693678da9efc443ef44 > > /var/lib/ceph/osd/ceph-1/current/6.39s1_head/NYAN__head_0BF243B9__6_ffffffffffffffff_1 > filesize: 4.0K > /var/lib/ceph/osd/ceph-1/current/6.39s1_head/NYAN__head_0BF243B9__6_ffffffffffffffff_1 > hexdump: 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > * > 00000560 > > osd.2 > path: > /var/lib/ceph/osd/ceph-2/current/6.39s3_head/NYAN__head_0BF243B9__6_ffffffffffffffff_3 > md5sum: ff6a7f77674e23fd7e3a0c11d7b36ed4 > > /var/lib/ceph/osd/ceph-2/current/6.39s3_head/NYAN__head_0BF243B9__6_ffffffffffffffff_3 > filesize: 4.0K > /var/lib/ceph/osd/ceph-2/current/6.39s3_head/NYAN__head_0BF243B9__6_ffffffffffffffff_3 > hexdump: 00000000 41 42 43 44 45 46 47 48 49 0a 00 00 00 00 00 00 > |ABCDEFGHI.......| > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > * > 00000560 > > osd.3 > path: > /var/lib/ceph/osd/ceph-3/current/6.39s0_head/NYAN__head_0BF243B9__6_ffffffffffffffff_0 > md5sum: ff6a7f77674e23fd7e3a0c11d7b36ed4 > > /var/lib/ceph/osd/ceph-3/current/6.39s0_head/NYAN__head_0BF243B9__6_ffffffffffffffff_0 > filesize: 4.0K > /var/lib/ceph/osd/ceph-3/current/6.39s0_head/NYAN__head_0BF243B9__6_ffffffffffffffff_0 > hexdump: 00000000 41 42 43 44 45 46 47 48 49 0a 00 00 00 00 00 00 > |ABCDEFGHI.......| > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > * > 00000560 > > osd.4 > path: > /var/lib/ceph/osd/ceph-4/current/6.39s4_head/NYAN__head_0BF243B9__6_ffffffffffffffff_4 > md5sum: ff6a7f77674e23fd7e3a0c11d7b36ed4 > > /var/lib/ceph/osd/ceph-4/current/6.39s4_head/NYAN__head_0BF243B9__6_ffffffffffffffff_4 > filesize: 4.0K > /var/lib/ceph/osd/ceph-4/current/6.39s4_head/NYAN__head_0BF243B9__6_ffffffffffffffff_4 > hexdump: 00000000 41 42 43 44 45 46 47 48 49 0a 00 00 00 00 00 00 > |ABCDEFGHI.......| > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > |................| > * > 00000560 > > > The erasure code profile used: > > jerasure-per-chunk-alignment=false > k=3 > m=2 > plugin=jerasure > ruleset-failure-domain=host > ruleset-root=default > technique=reed_sol_van > w=8 > > > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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