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List:       ceph-devel
Subject:    [ceph-devel] data distribution
From:       "sheng zheng" <zhengsheng2006 () gmail ! com>
Date:       2007-05-19 1:16:29
Message-ID: 79eb276e0705181816i1b1c0f3dw30bbfc4d274bd56f () mail ! gmail ! com
[Download RAW message or body]

hi,all
      recently,i always analyze the code about data distribution,but i
meet some problems.
  there are three members,stripe_size,stripe_count,object_size, in
class FileLayout.i want to know stripe_count means what and the
relation between stripe_size and object_size.
what's more ,i also want to understand stripeno,objectsetno means what
in function file_to_extents,
     in function oid Filer::file_to_extents(inode_t inode,
                            off_t offset, size_t len,
                            list<ObjectExtent>& extents,
			    objectrev_t rev)
{
   ......
    off_t blockno = cur / inode.layout.stripe_size;
    off_t stripeno = blockno / inode.layout.stripe_count;
    off_t stripepos = blockno % inode.layout.stripe_count;
    off_t objectsetno = stripeno / stripes_per_object;
    off_t objectno = objectsetno * inode.layout.stripe_count + stripepos;
  ......
}

thank for your help!

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