[sheepdog] [PATCH v4 0/3] use hyper volume to store containers and objects

[Robin Dong]

2013/12/12 Liu Yuan <namei.unix at gmail.com>

> On Thu, Dec 12, 2013 at 06:15:54PM +0800, Robin Dong wrote:
> > From: Robin Dong <sanbai at taobao.com>
> >
> > The old implemention of kv can only support small object (< 4MB), so we
> > use hyper volume ( up to 16PB ) to support large number of big object and
> > add lock to avoid race condition.
> >
> > After create a account, we will create a hyper volume vdi with the same
> name
> > and this vdi will stores inodes of buckets:
> >
> >   account vdi
> >
> +-----------+---+--------------------------+---+--------------------------+--
> >   |name: coly |...|bucket_inode (name: jetta)|...|bucket_inode (name:
> volvo)|..
> >
> +-----------+---+--------------------------+---+--------------------------+--
> >                                    |                             |
> >                                   /                              |
> >   bucket vdi                     /                               |
> >   +-----------------+-------+ <--                                |
> >   |name: coly/jetta |.......|                                    |
> >   +-----------------+-------+                                   /
> >                                bucket vdi                      /
> >                                +-----------------+------+ <----
> >                                | name: coly/volvo|......|
> >                                +-----------------+------+
> >
> > An account could stores number of "16PB / sizeof(struct bucket_inode)"
> buckets.
> >
> > The buckets has two vdis: one called bucket-vdi (named as bucket) and
> another
> > called data-vdi (named as "bucket/allocator").The bucket-vdi stores
> inodes of
> > objects and data-vdi stores the data of these objects:
> >
> >
> >                         --------------------- kv_onode
> -----------------------
> >                        |
>      |
> >   bucket vdi           v
>      v
> >
> +-----------------+--+---------------------------+--------------------------+
> >   |name: coly/fruit |..|kv_onode_hdr (name: banana)|onode_extent: start,
> count|
> >
> +-----------------+--+---------------------------+--------------------------+
> >                                                                    /
> >                                                                   /
> >                                                       ------------
> >                                                      /
> >                    data_vid                        v
> >                     +---------------------------+---+-----------------+
> >                     |name: coly/fruit/allocator |...|       data      |
> >                     +---------------------------+---+-----------------+
> >
> > The total size of data for objects in one bucket could reach 16PB
> recently, we
> > will add multi-data-vdi support for bucket in the future.
> >
> > TODO:
> >       1. add statistics for space in bytes for account/container.
> >       2. one bucket could use many hyper volumes to store data of
> objects.
> >       3. use kv_update_object() to upload large object parallely.
>
> I have tried the following steps:
>
>  1 create a user /yliu
>  2 create a container /yliu/computer
>  3 upload a 100M file A to /yliu/computer/test
>  4 update the same file A again and it succeded
>
> Then I found 'vdi list'
>
> yliu at ubuntu-precise:~/sheepdog$ dog/dog vdi list
>   Name        Id    Size    Used  Shared    Creation time   VDI id  Copies
>  Tag
>     yliu/computer/allocator     0   16 PB  204 MB  0.0 MB 2013-12-12 19:18
>    9ddb4     6
>
> note that 204 MB, I think it should be 104 MB because I overwrite the A
> with the
> same size.
>
>  5 delete the /yliu/computer/test
>
> yliu at ubuntu-precise:~/sheepdog$ dog/dog vdi list
>   Name        Id    Size    Used  Shared    Creation time   VDI id  Copies
>  Tag
>     yliu/computer/allocator     0   16 PB  104 MB  0.0 MB 2013-12-12 19:18
>    9ddb4     6
>
> Seems that I will have 100 MB never get released.
>
> yliu at ubuntu-precise:~/sheepdog$ curl -X GET
> http://localhost/v1/yliu/computer
>
> Says that I have no file in it!
>

As the swift API doc (
http://docs.openstack.org/api/openstack-object-storage/1.0/content/create-update-object.html)
says: the
second create operation is a update operation, but we will not support
update in this patchset. And, if I return CONFLICT when
users want to create a object twice, that will not be consistent to swift
API standard.

Any suggestion ?


> Thanks
> Yuan
>



-- 
--
Best Regard
Robin Dong
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