Aleksey Gutikov wrote a detailed response to a similar question last year, maybe this will help? http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-July/036318.html I haven't done much looking into this, but for your question, I believe the two option that control the size of objects on disk are the "rgw_obj_stripe_size", and the k value of the EC pool. rgw_obj_stripe_size (4MB) is the maximum size of a rados object that the RGW will create, so an S3 object larger than 4MB will be split into 4MB rados objects. An S3 object smaller than 4MB will not be padded as far as I know, and will exist as a single rados object of the same size as the S3 object. There is also a rgw_max_chunk_size parameter, but I'm not completely sure how it relates. I think S3 objects are striped and then chunked, so rgw_max_chunk_size = rgw_obj_stripe_size = 4MB results in 4MB rados objects. The K value of the EC pool defines the number of shards into which the rados object is split. In this case a k=10 will result in the shards on disk being 400KB ( 4MB / 10 ) or smaller. Cheers, Tom
-----Original Message----- From: Biswajeet Patra <biswajeet.patra@flipkart.com> Sent: 11 May 2020 12:51 To: ceph-users@ceph.io Cc: Priya Sehgal <priya.sehgal@flipkart.com> Subject: [ceph-users] Erasure coded pool queries
Hi, I have created an erasure coded pool and the below default parameters related to stripe sizes are present. "osd_pool_erasure_code_stripe_width": "4096" --> 4KB "rgw_obj_stripe_size": "4194304" --> 4MB Let say the k+m values are 10+5 for the erasure pool, and we upload an object of let say, size <4MB & another object of size >4MB. How will ceph break the object into chunks and store it & how many stripes will be created?
Regards, Biswajeet
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