On Fri, 6 May 2011, tsk wrote:
> Hi  Sage,
> 
> If I use librados:
> 
>     int create(const std::string& oid, bool exclusive);
>     int write(const std::string& oid, bufferlist& bl, size_t len, uint64_t 
> off);
>     int read(const std::string& oid, bufferlist& bl, size_t len, uint64_t 
> off);
> 
> MDS is not required to be running either?

Right.

> What does the oid mean,  is there any relation between oid and the
> object file name when it's dropped into an OSD server, like
> "current/0.c5_head/10000000004.000001ba_head"?
                     ^^^^^^^^^^^^^^^^^^^^
That part is the object name.  The _head bit is part of the snap revision 
tracking.

sage

> 
> 
> Thx very much!
> 
> 
> 2011/5/6 Sage Weil <[email protected]>:
> > On Fri, 6 May 2011, tsk wrote:
> >> 2011/5/6 Gregory Farnum <[email protected]>:
> >> > Nope, the MDS is only required for the POSIX-compliant Ceph layer.
> >> > -Greg
> >>
> >> May I know that who will maintain the rbd_image_info if there is no MDS?
> >> From where, the api int rbd_list(rados_ioctx_t io, char *names, size_t
> >> *size)  will get the data it want?
> >
> > The rbd image header is stored as just another object in the object store.
> >
> > sage
> >
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