Ceph RGW：数据的存储及寻址

RGW数据分布及寻址

RGW是一个对象处理网关。数据实际存储在ceph集群中。利用librados的接口，与ceph集群通信。RGW主要存储三类数据：元数据(metadata)、索引数据(bucket index)、数据(data)。这三类数据一般存储在不同的pool中，元数据也分多种元数据，存在不同的ceph pool中。

1、 Metadata
元数据信息包括：user，bucket，以及bucket.instance。其中：
user: 主要是对象存储的用户信息
bucket：主要维护bucket name与bucket instance id之间的映射信息
bucket.instance：维护了bucket instance信息

查看user的元数据如下：
radosgw-admin metadata list user:

//user相关的数据信息
[
    "ups3",
    "56789abcdef0123456789abcdef0123456789abcdef0123456789abcdef01234",
    "testx$9876543210abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
    "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
    "test",
    "testid"
]

radosgw-admin metadata get user:testid:

//获取用户testid的数据信息
{
    "key": "user:testid",
    "ver": {
        "tag": "_cAI-F3h-MuIUGNtXh2RgHlf",
        "ver": 1
    },
    "mtime": "2018-11-05 08:45:47.819290Z",
    "data": {
        "user_id": "testid",
        "display_name": "M. Tester",
        "email": "tester@ceph.com",
        "suspended": 0,
        "max_buckets": 1000,
        "auid": 0,
        "subusers": [],
        "keys": [
            {
                "user": "testid",
                "access_key": "0555b35654ad1656d804",
                "secret_key": "h7GhxuBLTrlhVUyxSPUKUV8r/2EI4ngqJxD7iBdBYLhwluN30JaT3Q=="
            }
        ],
        "swift_keys": [],
        "caps": [],
        "op_mask": "read, write, delete",
        "default_placement": "",
        "placement_tags": [],
        "bucket_quota": {
            "enabled": false,
            "check_on_raw": false,
            "max_size": -1,
            "max_size_kb": 0,
            "max_objects": -1
        },
        "user_quota": {
            "enabled": false,
            "check_on_raw": false,
            "max_size": -1,
            "max_size_kb": 0,
            "max_objects": -1
        },
        "temp_url_keys": [],
        "type": "rgw",
        "mfa_ids": [],
        "attrs": [
            {
                "key": "user.rgw.idtag",
                "val": ""
            }
        ]
    }
}

radosgw-admin metadata list bucket:

//bucket相关的元数据
[
    "first"
]

radosgw-admin metadata get bucket:first:

//bucket相关的元数据
{
    "key": "bucket:first",
    "ver": {
        "tag": "_Hx7x_Mor001U3WM8zfUAH6C",
        "ver": 1
    },
    "mtime": "2018-11-05 09:14:01.135441Z",
    "data": {
        "bucket": {
            "name": "first",
            "marker": "b96b1b04-cb67-4f0d-81ba-dbb70fd80678.4161.1",
            "bucket_id": "b96b1b04-cb67-4f0d-81ba-dbb70fd80678.4161.1",
            "tenant": "",
            "explicit_placement": {
                "data_pool": "",
                "data_extra_pool": "",
                "index_pool": ""
            }
        },
        "owner": "testid",
        "creation_time": "2018-11-05 09:13:59.491939Z",
        "linked": "true",
        "has_bucket_info": "false"
    }
}

radosgw-admin metadata list bucket.instance:

//bucket.instance相关的元数据
[
    "first:b96b1b04-cb67-4f0d-81ba-dbb70fd80678.4161.1"
]

radosgw-admin metadata get bucket.instance:first:{bucket_id}

//bucket.instance相关的元数据
{
    "key": "bucket.instance:first:b96b1b04-cb67-4f0d-81ba-dbb70fd80678.4161.1",
    "ver": {
        "tag": "_CUSoooY8ectqQPoZELOd_BE",
        "ver": 1
    },
    "mtime": "2018-11-05 09:14:01.132899Z",
    "data": {
        "bucket_info": {
            "bucket": {
                "name": "first",
                "marker": "b96b1b04-cb67-4f0d-81ba-dbb70fd80678.4161.1",
                "bucket_id": "b96b1b04-cb67-4f0d-81ba-dbb70fd80678.4161.1",
                "tenant": "",
                "explicit_placement": {
                    "data_pool": "",
                    "data_extra_pool": "",
                    "index_pool": ""
                }
            },
            "creation_time": "2018-11-05 09:13:59.491939Z",
            "owner": "testid",
            "flags": 0,
            "zonegroup": "98906840-3c9c-4402-beec-1616bcf2e07c",
            "placement_rule": "default-placement",
            "has_instance_obj": "true",
            "quota": {
                "enabled": false,
                "check_on_raw": false,
                "max_size": -1,
                "max_size_kb": 0,
                "max_objects": -1
            },
            "num_shards": 0,
            "bi_shard_hash_type": 0,
            "requester_pays": "false",
            "has_website": "false",
            "swift_versioning": "false",
            "swift_ver_location": "",
            "index_type": 0,
            "mdsearch_config": [],
            "reshard_status": 0,
            "new_bucket_instance_id": ""
        },
        "attrs": [
            {
                "key": "user.rgw.acl",
                "val": "AgKNAAAAAwIXAAAABgAAAHRlc3RpZAkAAABNLiBUZXN0ZXIEA2oAAAABAQAAAAYAAAB0ZXN0aWQPAAAAAQAAAAYAAAB0ZXN0aWQFAzsAAAACAgQAAAAAAAAABgAAAHRlc3RpZAAAAAAAAAAAAgIEAAAADwAAAAkAAABNLiBUZXN0ZXIAAAAAAAAAAAAAAAAAAAAA"
            },
            {
                "key": "user.rgw.idtag",
                "val": ""
            }
        ]
    }
}

2、Bucket Index
bucket index主要维护的是一个bucket中object的索引信息。一个bucket对应一个或多个rados object(开启bucket shards下)。维护的是一个key-val的map结构，map存放在object的omap(rocksdb)中，key对应的rgw object，val是关于rgw object的一些元数据信息，检索bucket的存放的object时，需要这些信息。omap也包含一个Header，其存放的是bucket account info，如此bucket中Object的个数，总的size等。
3、Data
rgw object内容，存放在一个或多个rados object中。rados object分为header和tail部分，header最多可以容纳512KB的数据，如果一个rgw object的大小小于512KB，那么只有header。否则剩余的数据会按照集群rados object的大小条带化分割成多个rados object。

数据检索路径

.rgw.root
{zone}.rgw.control
{zone}.rgw.meta
{zone}.rgw.log
{zone}.rgw.buckets.index
{zone}.rgw.buckets.data
{zone}.rgw.buckets.non-ec

在Pool： {zone}.rgw.meta利用namespace隔离多个存储空间：

root: bucket及bucket-instance
users.keys: 用户key
users.email:用户Email,object的key值=email
users.swift: swift账号
users.uid: s3用户及用户的Bucket信息
roles：
heap：

对于Pool: {zone}.rgw.log也包含多个namespace:

gc: 垃圾清理
lc: lifecycle
reshard:

当检索对象存储中的一个object时，会包含三个要素：user，bucket,object。user主要是RGW用于获取user id验证ACL；bucket及obejct用于确定object在pool中的位置。

User

user数据存储在{zone}.rgw.meta:users.uid中，如下：

[root@luminous1 ~]# rados -p upc.rgw.meta -N users.uid ls
ups3
ups3.buckets

包含两部分： ups3: user本身信息; ups3.buckets: 用户所属的bucket。

ups3：用户的基本信息，及ACL/Bucekt Quota/User Quota等；对应struct RGWUserInfo，定义于rgw_common.h。
ups3.buckets：用户所属的Buckets，key-value结构，存放于omap结构中；对应struct cls_user_bucket_entry，定义于rgw_common.h，数据操作如下：

# rados -p upc.rgw.meta  -N users.uid listomapkeys ups3.buckets
first
# rados -p upc.rgw.meta  -N users.uid getomapval ups3.buckets first ups3_bucket
Writing to ups3_bucket
# ceph-dencoder import ups3_bucket type cls_user_bucket_entry decode dump_json
    {
        "bucket": {
            "name": "first",
            "marker": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
            "bucket_id": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4"
        },
        "size": 1887,
        "size_rounded": 4096,
        "creation_time": "2019-07-22 02:48:17.945890Z",
        "count": 1,
        "user_stats_sync": "true"
    }

通过{uid}.buckets查到用户具有哪些buckets，并且这些bucket以下基本数据。

Bucket

Bucket信息存在在{zone}.rgw.meta:root中，如下：

[root@luminous1 ~]# rados -p upc.rgw.meta  -N root ls
.bucket.meta.first:1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4
first

first：记录了bucket与bucket_instance_id的对应关系，其对应于数据结构：struct RGWBucketEntryPoint
.bucket.meta.first:1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4： bucket instance；寻址方式：.bucket.meta.{tenant}:{bucket.name}:{bucket_id}；对应结构体：struct RGWBucketInfo。
其中Bucket ACL及IAM Policy存放在bucket instance object的attr中。如下：

# rados -p upc.rgw.meta  -N root get .bucket.meta.first:1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4 bucket_instance
通过读取bucket-instance object获取bucket的元数据信息
# ceph-dencoder import bucket_instance type RGWBucketInfo decode dump_json
{
    "bucket": {
        "name": "first",
        "marker": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
        "bucket_id": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
        "tenant": "",
        "explicit_placement": {
            "data_pool": "",
            "data_extra_pool": "",
            "index_pool": ""
        }
    },
    "creation_time": "2019-07-22 02:48:17.945890Z",
    "owner": "ups3",
    "flags": 0,
    "zonegroup": "2e7ac7db-8e21-43ed-9f3c-5a061ce1c7e3",
    "placement_rule": "default-placement",
    "has_instance_obj": "true",
    "quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    },
    "num_shards": 0,
    "bi_shard_hash_type": 0,
    "requester_pays": "false",
    "has_website": "false",
    "swift_versioning": "false",
    "swift_ver_location": "",
    "index_type": 0,
    "mdsearch_config": [],
    "reshard_status": 0,
    "new_bucket_instance_id": ""
}

获取Bucket ACL及IAM Policy数据如下：

ACL:

#rados -p upc.rgw.meta  -N root getxattr .bucket.meta.first:1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4 user.rgw.acl > acl
#ceph-dencoder type RGWAccessControlPolicy import acl decode dump_json
    {
        "acl": {
            "acl_user_map": [
                {
                    "user": "ups3",
                    "acl": 15
                }
            ],
            "acl_group_map": [],
            "grant_map": [
                {
                    "id": "ups3",
                    "grant": {
                        "type": {
                            "type": 0
                        },
                        "id": "ups3",
                        "email": "",
                        "permission": {
                            "flags": 15
                        },
                        "name": "S3 User",
                        "group": 0,
                        "url_spec": ""
                    }
                }
            ]
        },
        "owner": {
            "id": "ups3",
            "display_name": "S3 User"
        }
    }

Bucket Policy:

#rados -p upc.rgw.meta  -N root getxattr .bucket.meta.first:1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4 user.rgw.iam-policy
{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Principal": {"AWS": ["arn:aws:iam::usfolks:user/fred"]},
    "Action": "s3:PutObjectAcl",
    "Resource": [
      "arn:aws:s3:::first/*"
    ]
  }]
}

Object

Bucket Index:

Bucket Index： Bucket中包含的Object信息，都存放在一个或多个Object的 omap 中。此omap为一个key-value结构，key为object的名称，value对应struct rgw_bucket_dir_entry: cls_rgw_types.h。
Bucket Index Object：

pool： '{zone}.rgw.buckets.index'；
Object名称：1. 无shard下，'.dir.{bucket_id}'；2. shard，'.dir.{bucket_id}.{shard_id}'。

如下：

[root@luminous1 ~]# rados -p upc.rgw.buckets.index ls
.dir.1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4

在此bucket下，有一个object: ntp.conf:

[root@luminous1 ~]# rados -p upc.rgw.buckets.index listomapkeys .dir.1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4
ntp.conf

检索value:

[root@luminous1 ~]# rados -p upc.rgw.buckets.index getomapval .dir.1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4 ntp.conf object_key
Writing to object_key
[root@luminous1 ~]# ceph-dencoder type rgw_bucket_dir_entry import object_key decode dump_json
{
    "name": "ntp.conf",
    "instance": "",
    "ver": {
        "pool": 9,
        "epoch": 1
    },
    "locator": "",
    "exists": "true",
    "meta": {
        "category": 1,
        "size": 1887,
        "mtime": "2019-07-22 02:48:36.088530Z",
        "etag": "385c339c343a2495fd4479c992bfeb10",
        "owner": "ups3",
        "owner_display_name": "S3 User",
        "content_type": "text/plain",
        "accounted_size": 1887,
        "user_data": ""
    },
    "tag": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44192.174",
    "flags": 0,
    "pending_map": [],
    "versioned_epoch": 0
}

omap header记录了以下统计信息：

[root@luminous1 ~]# rados -p upc.rgw.buckets.index getomapheader .dir.1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4 index_object_header
Writing to index_object_header
[root@luminous1 ~]# ceph-dencoder type rgw_bucket_dir_header import index_object_header decode dump_json
{
    "ver": 33,
    "master_ver": 0,
    "stats": [
        1,
        {
            "total_size": 1887,
            "total_size_rounded": 4096,
            "num_entries": 1,
            "actual_size": 1887
        },
        3,
        {
            "total_size": 0,
            "total_size_rounded": 0,
            "num_entries": 0,
            "actual_size": 0
        },
        {
            "reshard_status": "none",
            "new_bucket_instance_id": "",
            "num_shards": -1
        }
    ]
}

Object Data:

对象存储object的数据存放在pool: {zone}.rgw.buckets.data中。object的构成及寻址分为以下两类：

一个RGW Object可以由一个或多个rados object构成。其中第一个 object 是此RGW 的 head 对象，主要包含一些元数据信息，如manifest, ACLs, content type, ETag, and user-defined metadata。这些metadata存放在此head 对象的xattr中。其中manifest描述了此rgw object在分布情况。同时，此head对象，最多可额外容纳4MB数据，如果RGW Object大小下于4MB，那么此 RGW Object就不会分片，只有此 head 对象。
如下检索：

[root@luminous1 ~]# rados -p upc.rgw.buckets.data listxattr 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_ntp.conf
user.rgw.acl
user.rgw.content_type
user.rgw.etag
user.rgw.idtag
user.rgw.manifest
user.rgw.pg_ver
user.rgw.source_zone
user.rgw.tail_tag
user.rgw.x-amz-content-sha256
user.rgw.x-amz-date
user.rgw.x-amz-meta-s3cmd-attrs
user.rgw.x-amz-storage-class

非multipart上传的object

目前bucket下有一个ntp.conf，<4MB。检索其manifest:

# rados -p upc.rgw.buckets.data getxattr 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_ntp.conf user.rgw.manifest > manifest

# ceph-dencoder type RGWObjManifest import manifest decode dump_json
{
    "objs": [],
    "obj_size": 1887,
    "explicit_objs": "false",
    "head_size": 1887,
    "max_head_size": 4194304,
    "prefix": ".Y3GeEIYgfMSqzZKW6xUfX-dPtPSH50f_",
    "rules": [
        {
            "key": 0,
            "val": {
                "start_part_num": 0,
                "start_ofs": 4194304,
                "part_size": 0,
                "stripe_max_size": 4194304,
                "override_prefix": ""
            }
        }
    ],
    "tail_instance": "",
    "tail_placement": {
        "bucket": {
            "name": "first",
            "marker": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
            "bucket_id": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
            "tenant": "",
            "explicit_placement": {
                "data_pool": "",
                "data_extra_pool": "",
                "index_pool": ""
            }
        },
        "placement_rule": "default-placement"
    }
}

如上：
max_head_size：表示head对象最大size；
head_size：表示当前head 对象size；
prefix：用于在rados中分片object的寻址。

RGW OBject ACL:

# rados -p upc.rgw.buckets.data getxattr 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_ntp.conf user.rgw.acl > object_acl
# ceph-dencoder type RGWAccessControlPolicy import object_acl decode dump_json
{
    "acl": {
        "acl_user_map": [
            {
                "user": "ups3",
                "acl": 15
            }
        ],
        "acl_group_map": [],
        "grant_map": [
            {
                "id": "ups3",
                "grant": {
                    "type": {
                        "type": 0
                    },
                    "id": "ups3",
                    "email": "",
                    "permission": {
                        "flags": 15
                    },
                    "name": "S3 User",
                    "group": 0,
                    "url_spec": ""
                }
            }
        ]
    },
    "owner": {
        "id": "ups3",
        "display_name": "S3 User"
    }
}

上传一个>4MB的 RGW Object，检索其manifest信息：

# dd if=/dev/zero of=./rgw_object bs=1024 count=13000
# s3cmd put rgw_object s3://first
# rados -p upc.rgw.buckets.data ls
    1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_rgw_object
    1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_.KaKMSwXh-SMiV-CYraCvEIUgz-_4tfD_1
    1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_.KaKMSwXh-SMiV-CYraCvEIUgz-_4tfD_3
    1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_ntp.conf
    1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_.KaKMSwXh-SMiV-CYraCvEIUgz-_4tfD_2
如上，Object分为4个对象，head，3个shadow分片。手动拼接如下，检查md5值相同：

# md5sum rgw_object 
    315e281f1e162ea635b56f7e0a2e25d8  rgw_object
# rados -p upc.rgw.buckets.data get 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_.KaKMSwXh-SMiV-CYraCvEIUgz-_4tfD_1 1
# cat 1 >> rgw_object_down 
# rados -p upc.rgw.buckets.data get 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_.KaKMSwXh-SMiV-CYraCvEIUgz-_4tfD_2 2
# cat 2 >> rgw_object_down 
# rados -p upc.rgw.buckets.data get 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_.KaKMSwXh-SMiV-CYraCvEIUgz-_4tfD_3 3
# cat 3 >> rgw_object_down 
# md5sum rgw_object_down 
    315e281f1e162ea635b56f7e0a2e25d8  rgw_object_down

Manifest信息：

[root@luminous1 ~]# rados -p upc.rgw.buckets.data getxattr 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_rgw_object user.rgw.manifest > manifest
[root@luminous1 ~]# ceph-dencoder type RGWObjManifest import manifest decode dump_json
{
    "objs": [],
    "obj_size": 13312000,
    "explicit_objs": "false",
    "head_size": 4194304,
    "max_head_size": 4194304,
    "prefix": ".KaKMSwXh-SMiV-CYraCvEIUgz-_4tfD_",
    "rules": [
        {
            "key": 0,
            "val": {
                "start_part_num": 0,
                "start_ofs": 4194304,
                "part_size": 0,
                "stripe_max_size": 4194304,
                "override_prefix": ""
            }
        }
    ],
    "tail_instance": "",
    "tail_placement": {
        "bucket": {
            "name": "first",
            "marker": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
            "bucket_id": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
            "tenant": "",
            "explicit_placement": {
                "data_pool": "",
                "data_extra_pool": "",
                "index_pool": ""
            }
        },
        "placement_rule": "default-placement"
    }
}

根据manifest检索对象：

- head： {bucket-id}_{object_name}，最大容纳4MB大小数据；
- shadow分片： {bucket-id}__shadow_{prefix}_{id} //id根据RGW Object大小及Rados Object(stripe_max_size)大小计算。

multipart object

对于一个大的RGW Object，会被切割成多个独立的RGW Object上传，称为multipart。multipar的优势是断点续传。s3接口默认切割大小为15MB。

在此，上传一个60MB大小的Object。

[root@luminous1 ~]# s3cmd put rgw_object s3://first
upload: 'rgw_object' -> 's3://first/rgw_object'  [part 1 of 4, 15MB] [1 of 1]
 15728640 of 15728640   100% in    1s    11.80 MB/s  done
upload: 'rgw_object' -> 's3://first/rgw_object'  [part 2 of 4, 15MB] [1 of 1]
 15728640 of 15728640   100% in    1s    13.61 MB/s  done
upload: 'rgw_object' -> 's3://first/rgw_object'  [part 3 of 4, 15MB] [1 of 1]
 15728640 of 15728640   100% in    1s    14.76 MB/s  done
upload: 'rgw_object' -> 's3://first/rgw_object'  [part 4 of 4, 920kB] [1 of 1]
 942080 of 942080   100% in    0s     6.38 MB/s  done

分成了四个部分上传，查看rados对象：

[root@luminous1 ~]# rados -p upc.rgw.buckets.data ls  | sort
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__multipart_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.1
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__multipart_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.2
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__multipart_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.3
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__multipart_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.4
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_rgw_object
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.1_1
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.1_2
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.1_3
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.2_1
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.2_2
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.2_3
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.3_1
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.3_2
1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4__shadow_rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd.3_3

包含了三类对象，head，multipart，shadow。

- head: {bucket_id}_{object_name}，只在xattr中存元数据，并不实际包含object data；
- multipart: multipart分段首对象，{bucket_id}__multipart_{prefix}.{multipart_id}，其中`multipart_id`根据`manifest`计算；
- shadow: 从属于multipart的分段对象，{bucket_id}__shadow_{prefix}.{multipart_id}_{shadow_id}，`shadow_id`：根据`manifest.rule.part_size`及 `manifest.rule.stripe_max_size`计算。

multipart下的manifest:

# rados -p upc.rgw.buckets.data getxattr 1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4_rgw_ob
# ceph-dencoder type RGWObjManifest import manifest decode dump_json
{
    "objs": [],
    "obj_size": 48128000,
    "explicit_objs": "false",
    "head_size": 0,
    "max_head_size": 0,
    "prefix": "rgw_object.2~BVWLOnCfNdXk4Tky2TB6hLD-VqgYbyd",
    "rules": [
        {
            "key": 0,
            "val": {
                "start_part_num": 1,
                "start_ofs": 0,
                "part_size": 15728640,
                "stripe_max_size": 4194304,
                "override_prefix": ""
            }
        },
        {
            "key": 47185920,
            "val": {
                "start_part_num": 4,
                "start_ofs": 47185920,
                "part_size": 942080,
                "stripe_max_size": 4194304,
                "override_prefix": ""
            }
        }
    ],
    "tail_instance": "",
    "tail_placement": {
        "bucket": {
            "name": "first",
            "marker": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
            "bucket_id": "1c60b268-0a5d-4718-ad02-e4b5bce824bf.44166.4",
            "tenant": "",
            "explicit_placement": {
                "data_pool": "",
                "data_extra_pool": "",
                "index_pool": ""
            }
        },
        "placement_rule": "default-placement"
    }
}

所有的object的检索是根据上述manifest信息构建object index:

- head_size： head对象大小，此处为0，表示无object data，只有xattr的元数据
- obj_size: RGW Object的原始大小
- prefix： object index前缀
- rules： multipart 及 shadow object检索信息。如在此manifest表示有4个multipart，其中1-3的大小为15MB，第4个为920KB
- rules.start_part_num: multipart 序号
- rules.part_size: 此multipart的分段大小
- rules.stripe_max_size: rados object的大小

在上以上的信息中，此RGW Object大小为48128000字节，分为4段，三段15MB，最后一段为920KB。同时每段存储在rados集群中的条带化大小为4MB。因此15MB大小的分段，也分为4个rados object，一个multipart首部，及3个shadow分片。920KB大小的分段只有一个multipart首部。

.rgw.root:

包含的都是zone,zonegroup,realm等信息

# rados -p .rgw.root ls
    period_config.b30c383b-25d3-46aa-8ef1-aedbd0196579
    default.realm
    periods.383529f4-1566-4061-a4ed-5a39188845dc.latest_epoch
    default.zone.b30c383b-25d3-46aa-8ef1-aedbd0196579
    zone_names.upc
    periods.383529f4-1566-4061-a4ed-5a39188845dc.1
    realms.b30c383b-25d3-46aa-8ef1-aedbd0196579
    default.zonegroup.b30c383b-25d3-46aa-8ef1-aedbd0196579
    realms_names.sh
    zonegroup_info.2e7ac7db-8e21-43ed-9f3c-5a061ce1c7e3
    realms.b30c383b-25d3-46aa-8ef1-aedbd0196579.control
    zone_info.1c60b268-0a5d-4718-ad02-e4b5bce824bf
    zonegroups_names.pd

最后编辑于：2020.04.20 23:51:28

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Ceph RGW：数据的存储及寻址

RGW数据分布及寻址

数据检索路径

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