> > > > Attached is an updated version of my rados kvm driver. I did the
> following
> > > > changes:
> > > >
> > >
> > > We tested it and it looks great. We were working on a native linux
> > > rados block device, and it'll be great if it would be compatible
> with
> > > the kvm one. There were some fairly minor issues that were related
> to
> > > the header. This is the modified metadata header that we're
> currently
> > > using:
Both implementations should definitely be compatible. - I will use this
header, too:
struct rbd_obj_header_ondisk {
char text[64];
char signature[4];
char version[8];
__le64 image_size;
__u8 obj_order;
__u8 crypt_type;
__u8 comp_type;
__le64 snap_seq;
__le16 snap_count;
__le64 snap_id[0];
} __attribute__((packed));
What is the purpose of snap_seq?
> Note that I changed objsize to obj_order, so that it'd be clear that
> the object size is a power of 2. Also, each of the fields should have
> be endian aware. We prefer using little-endian data, just so that it
> would be consistent across the ceph system.
I've already used little-endian, so that's no problem.
> Another issue is that the structure should be packed, so that it
> doesn't have any alignment problems.
> The original structure specified an array of MAX_SNAPS snap_id, where
> MAX_SNAPS is currently 4096. I'd rather have it set later on
> dynamically, as this is huge and quite a waste.
OK.
> The following was also changed:
>
> #define RBD_SUFFIX ".rbd"
>
> #define RBD_MAX_OBJ_NAME_SIZE 96
> #define RBD_MAX_SEG_NAME_SIZE 128
>
> I'd rather that the RBD_SUFFIX be a bit more meaningful. The object
> name size was reduced to 96 so that we don't overflow when adding the
> segment name.
RBD_SUFFIX is attached to every object-name, right?
Christian
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