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Hello, again, By talking about ‘write an object’, I mean by invoking the librados. Not via RDB or GW or CephFS. I want to understand how RADOS handle objects. Thanks Paul to remind me to refine my question. Thanks, Ming From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx]
On Behalf Of Liu, Ming (HPIT-GADSC) Hello, I have a dumb question about Ceph, hope someone can help me. I learned that on the bottom layer, there is a RADOS, which is an object storage layer. So as for me, it is basically an interface that one can save a key/value object in each write operation. And each object will finally map to a physical
file in ODS’s local file system. So my question is, if I write an object with size as 10 bytes, will OSD finally create a 10-bytes file on its local file system? Or it will find a file in OSD’s local file system and append this object into that file?
And if I have an object that is 1G in size, I think Ceph will strip that, which will physically have N files on OSD’s local file system, and there should be a fix size of these files up to the block size defined as the max size of an object,
is this correct? How OSD find the corresponding file to read the given object? Using object-ID to find the corresponding file name? And, the metadata of an object is also save in the same physical file? How this file is structured? I hope there will be
some details here. I read various papers but cannot figure this out clearly, it talks many about how CURSH map an object into OSDs, but not much description about how that object map into OSD’s local file system. If there is such description, would someone
kindly point out for me to read? Any help will be very appreciated. Thanks in advance. Thanks, Ming |
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