[lustre-devel] question about mapping of file to object

[Dilger, Andreas]

On 2013/12/10 1:56 AM, "pierce liu" <netgridx at gmail.com> wrote:
>I am a new beginner of lusterfs. During browsing the source code, I am
>puzzled about how to map file to multi-object. Is there any document for
>that, or how to trace the code.

Hi Pierce,
there is a general overview of Lustre at Wikipedia.  There are also quite
a few presentations available online, and videos on Youtube describing
the basics of Lustre.

The filesystem namespace is held on the MDT.  Each inode has a "Logical
Object Volume" (LOV) xattr (struct lov_mds_md_v1 or struct lov_mds_md_v3)
that describes the mapping to OST objects.  When a client opens a file on
the MDT, the LOV xattr is returned to the client, which describes they
layout of the file (stripe count, stripe size) and the OST objects that
hold the file data.  After that point, the client does IO directly to the
OSTs.

>BTW, is this mailing list the effective one for lusterfs, or we have
>other list?

This list is fine.

Cheers, Andreas
-- 
Andreas Dilger

Lustre Software Architect
Intel High Performance Data Division