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

[Liu Yuan]

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!

Thanks
Yuan