Ceph 之RGW Data Layout

本文轉載自查看原文 2019-11-21 21:31 848 Ceph/ 分布式系統/ 存儲

Overview
RGW Pools
RGW Object
References

Overview

RGW 中三個基本概念：user， bucket， object。通過分析RGW data layout，可以清楚對象存儲的三個基本概念是怎樣在RGW 中實現的。

RGW 中數據分三種類型：

data: 每個RGW object 會保存在一個或多個Rados object(s)
metadata: user, bucket, bucket.instance
bucket index: 單獨作為一種metadata
RGW 的數據在RADOS 層以三種形式存在：rados對象（data 部分），rados 對象擴展屬性xattr，rados 對象的omap中。

metadata

RGW metadata分為：

user：保存user 信息
bucket：維護一組bucket name 和bucket instance id 的映射
bucket.instance：保存bucket instance 信息
otp：N 版新增，otp (one-time password) 信息。根據虛擬或硬件Multi-Factor Authentication (MFA) 設備，基於已經時間同步的otp 算法生成一個密碼。
metadata list，可以看到是上面列出的四種類型：

[root@stor14 build]# bin/radosgw-admin metadata list -c ceph.conf
[
    "bucket",
    "bucket.instance",
    "otp",
    "user"
]

查看user 下都有什么：

[root@stor14 build]# bin/radosgw-admin metadata list user -c ceph.conf
[
    "56789abcdef0123456789abcdef0123456789abcdef0123456789abcdef01234",
    "bl_deliver",
    "testx$9876543210abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
    "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
    "user1",
    "test",
    "testid",
    "ms_sync"
]

list bucket.instance 看下，一般一個bucket 對應一個bucket.instance

[root@stor14 build]# bin/radosgw-admin metadata list bucket.instance -c ceph.conf
[
"bltest1:e34456f0-d371-4384-9007-70c60563fb0b.4281.17",
"test1:e34456f0-d371-4384-9007-70c60563fb0b.4281.15"
]

接着看下bltest1:e34456f0-d371-4384-9007-70c60563fb0b.4281.17 這個bucket.instance

[root@stor14 build]# bin/radosgw-admin metadata get bucket.instance:bltest1:e34456f0-d371-4384-9007-70c60563fb0b.4281.17 -c ceph.conf
{
    "key": "bucket.instance:bltest1:e34456f0-d371-4384-9007-70c60563fb0b.4281.17",
    "ver": {
        "tag": "_UHAkf8NRdh_eXm7CqYsFNA8",
        "ver": 1
    },
    "mtime": "2019-11-20 07:53:39.493618Z",
    "data": {
        "bucket_info": {
            "bucket": {
                "name": "bltest1",
                "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4281.17",
                "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4281.17",
                "tenant": "",
                "explicit_placement": {
                    "data_pool": "",
                    "data_extra_pool": "",
                    "index_pool": ""
                }
            },
            "creation_time": "2019-11-20 07:53:39.399284Z",
            "owner": "user1",
            "flags": 0,
            "zonegroup": "513b96de-2450-4292-a86a-314abbe29766",
            "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": "AgKBAAAAAwISAAAABQAAAHVzZXIxBQAAAHVzZXIxBANjAAAAAQEAAAAFAAAAdXNlcjEPAAAAAQAAAAUAAAB1c2VyMQUDNgAAAAICBAAAAAAAAAAFAAAAdXNlcjEAAAAAAAAAAAICBAAAAA8AAAAFAAAAdXNlcjEAAAAAAAAAAAAAAAAAAAAA"
            }
        ]
    }
}

獲取bltest1 這個存儲桶相關信息：

[root@stor14 build]# bin/radosgw-admin metadata get bucket:bltest1 -c ceph.conf
{
    "key": "bucket:bltest1",
    "ver": {
        "tag": "_Sia7A02mjQlrvVkymKa_y2G",
        "ver": 1
    },
    "mtime": "2019-11-20 07:53:39.560897Z",
    "data": {
        "bucket": {
            "name": "bltest1",
            "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4281.17",
            "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4281.17",
            "tenant": "",
            "explicit_placement": {
                "data_pool": "",
                "data_extra_pool": "",
                "index_pool": ""
            }
        },
        "owner": "user1",
        "creation_time": "2019-11-20 07:53:39.399284Z",
        "linked": "true",
        "has_bucket_info": "false"
    }
}

由於我們沒有做MFA 相關配置，otp 目前為空：

[root@stor14 build]# bin/radosgw-admin metadata list otp -c ceph.conf
[]

bucket index

bucket index 是一類特殊的metadata，通過bucket index 我們可以list 指定存儲桶下的所有rgw 對象。
bucket index 對象保存在存儲池 .rgw.buckets.index，名為 “.dir. ” 的rados object。

bucket index 維護了一個k-v map，

k-v map本身保存在rados object(s) 關聯的omap 中。在不啟用shard 時，一個存儲桶會對應一個rados object；若shard 后，一個存儲桶可能會對應多個index rados objects。
omap 的key 為各rgw object name，omap value 這些rgw object 的一些基本元數據，如list bucket 時展示的元數據。
每個omap 有一個header，在header 中保存一些bucket的統計信息（對象數，總大小等）?

list 一下bucket index 對象（rados object）：

[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.buckets.index
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.15
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.17

可以看到兩個index objects，此時default zone 下只有兩個存儲桶。

[root@stor14 build]# bin/radosgw-admin bucket list -c ceph.conf
[
    "test1",
    "bltest1"
]

其中對應存儲桶bltest1

[root@stor14 build]# bin/radosgw-admin bucket stats --bucket test1 -c ceph.conf
{
    "bucket": "test1",
    "tenant": "",
    "zonegroup": "513b96de-2450-4292-a86a-314abbe29766",
    "placement_rule": "default-placement",
    "explicit_placement": {
        "data_pool": "",
        "data_extra_pool": "",
        "index_pool": ""
    },
    "id": "e34456f0-d371-4384-9007-70c60563fb0b.4281.15",
    "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4281.15", # 由marker可以看到對應index 對象 .dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.15
    "index_type": "Normal",
    "owner": "user1",
    "ver": "0#3",
    "master_ver": "0#0",
    "mtime": "2019-11-20 07:53:38.898208Z",
    "max_marker": "0#",
    "usage": {
        "rgw.main": {
            "size": 10279,
            "size_actual": 16384,
            "size_utilized": 10279,
            "size_kb": 11,
            "size_kb_actual": 16,
            "size_kb_utilized": 11,
            "num_objects": 2
        }
    },
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    }
}

listomapkeys 看下

[root@stor14 build]# bin/rados -c ceph.conf listomapkeys .dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.15 -p default.rgw.buckets.index
dcj1
dcj2
可以看到omap key：dcj1 和dcj2，再listomapvals 看下，此時可以看2個RGW 對象

[root@stor14 build]# bin/rados -c ceph.conf listomapvals .dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.15 -p default.rgw.buckets.index
dcj1
value (218 bytes) :
00000000  08 03 d4 00 00 00 04 00  00 00 64 63 6a 31 01 00  |..........dcj1..|
00000010  00 00 00 00 00 00 01 07  03 6e 00 00 00 01 ca 13  |.........n......|
00000020  00 00 00 00 00 00 06 f1  d4 5d f1 9c e0 0e 20 00  |.........].... .|
00000030  00 00 38 30 64 34 36 33  66 36 32 35 65 39 32 37  |..80d463f625e927|
00000040  39 31 39 35 65 30 37 34  65 35 34 65 65 63 64 31  |9195e074e54eecd1|
00000050  34 39 05 00 00 00 75 73  65 72 31 05 00 00 00 75  |49....user1....u|
00000060  73 65 72 31 0a 00 00 00  74 65 78 74 2f 70 6c 61  |ser1....text/pla|
00000070  69 6e ca 13 00 00 00 00  00 00 00 00 00 00 08 00  |in..............|
00000080  00 00 53 54 41 4e 44 41  52 44 00 00 00 00 00 00  |..STANDARD......|
00000090  00 00 00 01 01 02 00 00  00 08 01 01 2c 00 00 00  |............,...|
000000a0  65 33 34 34 35 36 66 30  2d 64 33 37 31 2d 34 33  |e34456f0-d371-43|
000000b0  38 34 2d 39 30 30 37 2d  37 30 63 36 30 35 36 33  |84-9007-70c60563|
000000c0  66 62 30 62 2e 34 32 36  37 2e 35 34 00 00 00 00  |fb0b.4267.54....|
000000d0  00 00 00 00 00 00 00 00  00 00                    |..........|
000000da


dcj2
value (220 bytes) :
00000000  08 03 d6 00 00 00 04 00  00 00 64 63 6a 32 01 00  |..........dcj2..|
00000010  00 00 00 00 00 00 01 07  03 6e 00 00 00 01 5d 14  |.........n....].|
00000020  00 00 00 00 00 00 54 2e  d5 5d 49 86 f8 2a 20 00  |......T..]I..* .|
00000030  00 00 38 39 36 39 39 37  63 37 63 37 62 64 64 61  |..896997c7c7bdda|
00000040  30 38 61 62 30 39 62 38  35 34 36 32 33 61 30 30  |08ab09b854623a00|
00000050  30 30 05 00 00 00 75 73  65 72 31 05 00 00 00 75  |00....user1....u|
00000060  73 65 72 31 0a 00 00 00  74 65 78 74 2f 70 6c 61  |ser1....text/pla|
00000070  69 6e 5d 14 00 00 00 00  00 00 00 00 00 00 08 00  |in].............|
00000080  00 00 53 54 41 4e 44 41  52 44 00 00 00 00 00 00  |..STANDARD......|
00000090  00 00 00 01 01 02 00 00  00 08 01 02 2e 00 00 00  |................|
000000a0  65 33 34 34 35 36 66 30  2d 64 33 37 31 2d 34 33  |e34456f0-d371-43|
000000b0  38 34 2d 39 30 30 37 2d  37 30 63 36 30 35 36 33  |84-9007-70c60563|
000000c0  66 62 30 62 2e 34 35 36  34 2e 34 30 30 36 00 00  |fb0b.4564.4006..|
000000d0  00 00 00 00 00 00 00 00  00 00 00 00              |............|
000000dc

一般一個存儲桶對應一個rados object，H版之后加入shard 后，也可能會一個存儲桶對應多個rados objects。目前N 版已經可以做到auto reshard。我們通過配置rgw_override_bucket_index_max_shards = 5 將新建存儲桶的shard 初始化為5 分片

新建存儲桶test2

[root@stor14 build]# s3cmd mb s3://test2
Bucket 's3://test2/' created
可以看到max_marker 有5個：0#,1#,2#,3#,4#
[root@stor14 build]# bin/radosgw-admin bucket stats --bucket test2 -c ceph.conf
{
    "bucket": "test2",
    "tenant": "",
    "zonegroup": "513b96de-2450-4292-a86a-314abbe29766",
    "placement_rule": "default-placement",
    "explicit_placement": {
        "data_pool": "",
        "data_extra_pool": "",
        "index_pool": ""
    },
    "id": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
    "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
    "index_type": "Normal",
    "owner": "user1",
    "ver": "0#1,1#1,2#1,3#1,4#1",
    "master_ver": "0#0,1#0,2#0,3#0,4#0",
    "mtime": "2019-11-20 12:26:38.164727Z",
    "max_marker": "0#,1#,2#,3#,4#",
    "usage": {},
    "bucket_quota": {
        "enabled": false,
        "check_on_raw": false,
        "max_size": -1,
        "max_size_kb": 0,
        "max_objects": -1
    }
}

此時除了之前的2個 index objects 外，多出來了5個對象，名為 .dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.

[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.buckets.index
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.1
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.3
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.2
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.4
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.15
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.0
.dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.17

我們上傳一個對象jcd1 至新建的存儲桶test2

[root@stor14 build]# s3cmd ls s3://test2
[root@stor14 build]# s3cmd put ./ceph.conf s3://test2/jcd1
upload: './ceph.conf' -> 's3://test2/jcd1'  [1 of 1]
 5255 of 5255   100% in    0s    26.82 kB/s  done
[root@stor14 build]# bin/rados -c ceph.conf listomapkeys .dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.0 -p default.rgw.buckets.index

[root@stor14 build]# bin/rados -c ceph.conf listomapkeys .dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.1 -p default.rgw.buckets.index

[root@stor14 build]# bin/rados -c ceph.conf listomapkeys .dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.2 -p default.rgw.buckets.index
jcd1
[root@stor14 build]# bin/rados -c ceph.conf listomapkeys .dir.e34456f0-d371-4384-9007-70c60563fb0b.4848.1.3 -p default.rgw.buckets.index

可以看到上傳的對象在分片2 中。
默認情況下bucket index obj 並沒有attr 信息：

[root@stor14 build]# bin/rados -c ceph.conf listxattr .dir.e34456f0-d371-4384-9007-70c60563fb0b.4281.15 -p default.rgw.buckets.index

一般來說單shard 保存10萬-15萬對象為宜，shard 數也不是越多越好，過多的shard會導致部分類似list bucket的操作消耗大量底層存儲IO，導致部分請求耗時過長。

data

每個RGW object 會保存在一個或多個rados obj 中。下面會詳細介紹RGW Object 的layout。

RGW Pools

RGW 使用各種 pool 來專門存放特定類型的數據, zone 所使用的存儲池的命名規則 {zone}.rgw.{functions} 。

可以看到default zone下配置的存儲池：

[root@stor14 build]# bin/radosgw-admin zone get -c ceph.conf
{
    "id": "e34456f0-d371-4384-9007-70c60563fb0b",
    "name": "default",
    "domain_root": "default.rgw.meta:root",
    "control_pool": "default.rgw.control",
    "gc_pool": "default.rgw.log:gc",
    "lc_pool": "default.rgw.log:lc",
    "bl_pool": "default.rgw.log:bl",
    "log_pool": "default.rgw.log",
    "intent_log_pool": "default.rgw.log:intent",
    "usage_log_pool": "default.rgw.log:usage",
    "reshard_pool": "default.rgw.log:reshard",
    "user_keys_pool": "default.rgw.meta:users.keys",
    "user_email_pool": "default.rgw.meta:users.email",
    "user_swift_pool": "default.rgw.meta:users.swift",
    "user_uid_pool": "default.rgw.meta:users.uid",
    "otp_pool": "default.rgw.otp", # metadata 中提到的One-Time Password 用的存儲池
    "system_key": {
        "access_key": "ms_sync",
        "secret_key": "ms_sync"
    },
    "bl_deliver_key": {
        "access_key": "bl_deliver",
        "secret_key": "bl_deliver"
    },
    "placement_pools": [
        {
            "key": "default-placement",
            "val": {
                "index_pool": "default.rgw.buckets.index", 
                "storage_classes": {
                    "STANDARD": {
                        "data_pool": "default.rgw.buckets.data"
                    }
                },
                "data_extra_pool": "default.rgw.buckets.non-ec",
                "index_type": 0
            }
        }
    ],
    "metadata_heap": "",
    "realm_id": "5f47bd7c-94a1-48f5-8c51-5bb8f7075425"
}

重要的RGW Pools：

.rgw.root - 保存 zone,zg,realm,period 相關的信息
zone.rgw.control - librados 提供的 watch-notify 機制保證緩存一致性,如 notify.
zone.rgw.log - 記錄不同的日志,--namespace usage, gc, lc, bl
- gc: 用於垃圾回收的
- lc: 用於lifecycle
- bl：用於bucket logging
zone.rgw.buckets.data ,數據池
zone.rgw.buckets.extra ,現在叫 rgw.buckets.non-ec ,multipart upload 過程中的臨時數據會放這里。

zone.rgw.buckets.index - 存儲 bucket 中對象的索引對象： “.dir. ”

zone.rgw.meta: 對象存儲元數據池, --namespace users, root
- root： .bucket.meta. : # see put_bucket_instance_info()
- users.id：Contains both per-user information (RGWUserInfo) in “ ” objects and per-user lists of buckets in omaps of “ .buckets” objects. The “ ” may contain the tenant if non-empty
- users.keys：允許RGW在認證時通過access-key 去找到user id
  看下 .rgw.meta 池

[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.meta -N root
test1
.bucket.meta.test2:e34456f0-d371-4384-9007-70c60563fb0b.4848.1
.bucket.meta.bltest1:e34456f0-d371-4384-9007-70c60563fb0b.4281.17
bltest1
.bucket.meta.test1:e34456f0-d371-4384-9007-70c60563fb0b.4281.15
test2
[root@stor14 build]# bin/rados -c ceph.conf listxattr test1 -p default.rgw.meta -N root
ceph.objclass.version
[root@stor14 build]# bin/rados -c ceph.conf listxattr .bucket.meta.test1:e34456f0-d371-4384-9007-70c60563fb0b.4281.15 -p default.rgw.meta -N root
ceph.objclass.version
user.rgw.acl

看下users.uid

[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.meta -N users.uid
56789abcdef0123456789abcdef0123456789abcdef0123456789abcdef01234
bl_deliver
testx$9876543210abcdef0123456789abcdef0123456789abcdef0123456789abcdef
0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
user1
test
testid
ms_sync
user1.buckets # *****
 
[root@stor14 build]# bin/radosgw-admin user list -c ceph.conf
[
    "56789abcdef0123456789abcdef0123456789abcdef0123456789abcdef01234",
    "bl_deliver",
    "testx$9876543210abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
    "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
    "user1",
    "test",
    "testid",
    "ms_sync"
]

可以看到users.uid 中除了oss user，還有一個user1.buckets
“Contains both per-user information (RGWUserInfo) in “ ” objects and per-user lists of buckets in omaps of “ .buckets” objects. The “ ” may contain the tenant if non-empty”

其實這個user1.buckets 對象是一個非常重要的對象。通過bucket index obj 可以list 某個存儲桶中的rgw objects，如何list 某個對象存儲用戶下的存儲桶呢？答案就是這個 .buckets 對象的omap 中list，指定用戶下的所有存儲桶信息會在 .buckets 對象的omap 中保存：

[root@stor14 build]# bin/rados -c ceph.conf listomapkeys user1.buckets -p default.rgw.meta -N users.uid
bltest1
test1
test2
[root@stor14 build]# bin/rados -c ceph.conf listomapvals user1.buckets -p default.rgw.meta -N users.uid
bltest1
value (172 bytes) :
00000000  09 05 a6 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000010  00 00 03 f1 d4 5d 00 00  00 00 00 00 00 00 07 03  |.....]..........|
00000020  77 00 00 00 07 00 00 00  62 6c 74 65 73 74 31 00  |w.......bltest1.|
00000030  00 00 00 2c 00 00 00 65  33 34 34 35 36 66 30 2d  |...,...e34456f0-|
00000040  64 33 37 31 2d 34 33 38  34 2d 39 30 30 37 2d 37  |d371-4384-9007-7|
00000050  30 63 36 30 35 36 33 66  62 30 62 2e 34 32 38 31  |0c60563fb0b.4281|
00000060  2e 31 37 2c 00 00 00 65  33 34 34 35 36 66 30 2d  |.17,...e34456f0-|
00000070  64 33 37 31 2d 34 33 38  34 2d 39 30 30 37 2d 37  |d371-4384-9007-7|
00000080  30 63 36 30 35 36 33 66  62 30 62 2e 34 32 38 31  |0c60563fb0b.4281|
00000090  2e 31 37 00 00 00 00 00  00 00 00 00 00 00 00 00  |.17.............|
000000a0  00 00 00 01 03 f1 d4 5d  26 99 cc 17              |.......]&...|
000000ac
test1
value (170 bytes) :
00000000  09 05 a4 00 00 00 00 00  00 00 27 28 00 00 00 00  |..........'(....|
00000010  00 00 02 f1 d4 5d 02 00  00 00 00 00 00 00 07 03  |.....]..........|
00000020  75 00 00 00 05 00 00 00  74 65 73 74 31 00 00 00  |u.......test1...|
00000030  00 2c 00 00 00 65 33 34  34 35 36 66 30 2d 64 33  |.,...e34456f0-d3|
00000040  37 31 2d 34 33 38 34 2d  39 30 30 37 2d 37 30 63  |71-4384-9007-70c|
00000050  36 30 35 36 33 66 62 30  62 2e 34 32 38 31 2e 31  |60563fb0b.4281.1|
00000060  35 2c 00 00 00 65 33 34  34 35 36 66 30 2d 64 33  |5,...e34456f0-d3|
00000070  37 31 2d 34 33 38 34 2d  39 30 30 37 2d 37 30 63  |71-4384-9007-70c|
00000080  36 30 35 36 33 66 62 30  62 2e 34 32 38 31 2e 31  |60563fb0b.4281.1|
00000090  35 00 00 00 00 00 00 00  00 00 40 00 00 00 00 00  |5.........@.....|
000000a0  00 01 02 f1 d4 5d 74 a9  42 32                    |.....]t.B2|
000000aa
test2
value (168 bytes) :
00000000  09 05 a2 00 00 00 00 00  00 00 87 14 20 02 00 00  |............ ...|
00000010  00 00 fd 30 d5 5d 05 00  00 00 00 00 00 00 07 03  |...0.]..........|
00000020  73 00 00 00 05 00 00 00  74 65 73 74 32 00 00 00  |s.......test2...|
00000030  00 2b 00 00 00 65 33 34  34 35 36 66 30 2d 64 33  |.+...e34456f0-d3|
00000040  37 31 2d 34 33 38 34 2d  39 30 30 37 2d 37 30 63  |71-4384-9007-70c|
00000050  36 30 35 36 33 66 62 30  62 2e 34 38 34 38 2e 31  |60563fb0b.4848.1|
00000060  2b 00 00 00 65 33 34 34  35 36 66 30 2d 64 33 37  |+...e34456f0-d37|
00000070  31 2d 34 33 38 34 2d 39  30 30 37 2d 37 30 63 36  |1-4384-9007-70c6|
00000080  30 35 36 33 66 62 30 62  2e 34 38 34 38 2e 31 00  |0563fb0b.4848.1.|
00000090  00 00 00 00 00 00 00 00  20 20 02 00 00 00 00 01  |........  ......|
000000a0  fd 30 d5 5d 57 b6 f2 3a                           |.0.]W..:|
000000a8

RGW Object

一個RGW Object 有一個或多個Rados Object 組成。RGW object 邏輯上一般分為head 和tail。

其中head( object logiccal head, olh)，元數據會保存在擴展屬性xattr中:

head 保存在單個 RADOS object
head 是有固定的大小的(rgw_max_chunk_size 默認 4M)
內容可變保存 RGW object 的元數據
- ACLs
- Manifest
- Conten-Type
- ETag
- User-Defined Metadata(保存在 xattrs)

tail 部分:

內容不可變
對於小於 rgw_max_chunk_size 的 rgw-object 沒有 tail
對於multipart 上傳的對象，tail 分multipart （每個part 的第一個rados對象）和shadow
tail 被分隔成若干個 part，單個 part 保存 rgw-object 的連續數據,每個 part 默認 15M
普通的 rgw-object 只有單個 part(但 part 內可以有很多的 stripe),對於 multipart - 上傳的 rgw-object 就有多個 part(最后一個 part 可能比較小)。注意 part 還是邏輯上的
每個 part 都是 striped, striped part 由默認的 stripe size,每個 stripe part 映射到 rados-object,stripe 和 rados-object 一一對應

驗證一下：

[root@stor14 build]# s3cmd put ./4MB s3://test2
upload: './4MB' -> 's3://test2/4MB'  [1 of 1]
 4194304 of 4194304   100% in    0s     8.14 MB/s  done
[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.buckets.data
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_jcd1
e34456f0-d371-4384-9007-70c60563fb0b.4281.15_dcj2
e34456f0-d371-4384-9007-70c60563fb0b.4281.15_dcj1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_4MB
[root@stor14 build]# dd if=/dev/zero of=./5MB count=5 bs=1024k
記錄了5+0 的讀入
記錄了5+0 的寫出
5242880字節(5.2 MB)已復制，0.00357833 秒，1.5 GB/秒
[root@stor14 build]# s3cmd put ./5MB s3://test2
upload: './5MB' -> 's3://test2/5MB'  [1 of 1]
 5242880 of 5242880   100% in    0s     7.18 MB/s  done
[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.buckets.data
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_jcd1
e34456f0-d371-4384-9007-70c60563fb0b.4281.15_dcj2
e34456f0-d371-4384-9007-70c60563fb0b.4281.15_dcj1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_4MB
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_.lWnArC6BcKPkRjbGf-B0q23BSpxjql1_1

我們先后有上傳了2個對象:一個4MB，一個5MB，大小同對象名。可以看到，超過4MB 之后，RGW 對象分為了2 個RADOS 對象，其中
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB 為head，e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_.lWnArC6BcKPkRjbGf-B0q23BSpxjql1_1 為tail。
查看2個rados obj 的大小：

[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB mtime 2019-11-20 20:49:11.000000, size 4194304
[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_.lWnArC6BcKPkRjbGf-B0q23BSpxjql1_1
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_.lWnArC6BcKPkRjbGf-B0q23BSpxjql1_1 mtime 2019-11-20 20:49:11.000000, size 1048576

可以看到，head obj size=4194304，也即一個stripe 大小，加上tail obj size=1048576，正好等於RGW raw obj 的大小5242880。
我們可以在head 中可以list 元數據

[root@stor14 build]# bin/rados -c ceph.conf listxattr e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB -p default.rgw.buckets.data
user.rgw.acl
user.rgw.content_type
user.rgw.etag
user.rgw.idtag
user.rgw.manifest # manifest 保存了RGW 對象的layout，可以看作是RGW 對象到RADOS 對象的映射關系圖。
user.rgw.pg_ver
user.rgw.source_zone
user.rgw.storage_class
user.rgw.tail_tag
user.rgw.x-amz-content-sha256
user.rgw.x-amz-date
user.rgw.x-amz-meta-s3cmd-attrs

看下manifest

[root@stor14 build]# bin/rados -c ceph.conf getxattr e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB -p default.rgw.buckets.data user.rgw.manifest > /tmp/m

decode 為可讀：

[root@stor14 build]# bin/ceph-dencoder type RGWObjManifest import /tmp/m decode dump_json
{
    "objs": [],
    "obj_size": 5242880,
    "explicit_objs": "false",
    "head_size": 4194304, # head 大小
    "max_head_size": 4194304,
    "prefix": ".lWnArC6BcKPkRjbGf-B0q23BSpxjql1_", # 可以在tail obj 上看到，關聯各tail objects
    "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": "test2",
            "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1", 
            "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
            "tenant": "",
            "explicit_placement": {
                "data_pool": "",
                "data_extra_pool": "",
                "index_pool": ""
            }
        },
        "placement_rule": "default-placement"
    },
    "begin_iter": {
        "part_ofs": 0,
        "stripe_ofs": 0,
        "ofs": 0,
        "stripe_size": 4194304,
        "cur_part_id": 0,
        "cur_stripe": 0,
        "cur_override_prefix": "",
        "location": {
            "placement_rule": "default-placement",
            "obj": {
                "bucket": {
                    "name": "test2",
                    "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "tenant": "",
                    "explicit_placement": {
                        "data_pool": "",
                        "data_extra_pool": "",
                        "index_pool": ""
                    }
                },
                "key": {
                    "name": "5MB",
                    "instance": "",
                    "ns": ""
                }
            },
            "raw_obj": {
                "pool": "",
                "oid": "",
                "loc": ""
            },
            "is_raw": false
        }
    },
    "end_iter": {
        "part_ofs": 4194304,
        "stripe_ofs": 4194304,
        "ofs": 5242880,
        "stripe_size": 1048576,
        "cur_part_id": 0,
        "cur_stripe": 1,
        "cur_override_prefix": "",
        "location": {
            "placement_rule": "default-placement",
            "obj": {
                "bucket": {
                    "name": "test2",
                    "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "tenant": "",
                    "explicit_placement": {
                        "data_pool": "",
                        "data_extra_pool": "",
                        "index_pool": ""
                    }
                },
                "key": {
                    "name": ".lWnArC6BcKPkRjbGf-B0q23BSpxjql1_1", # 當前shadow tail obj的key：manifest.prefix+stripe_id
                    "instance": "",
                    "ns": "shadow"  # tail 類型為shadow
                }
            },
            "raw_obj": {
                "pool": "",
                "oid": "",
                "loc": ""
            },
            "is_raw": false
        }
    }
}

manifest 中begin_iter 和end_iter的ofset 值及cur_part_id、cur_stripe_id，這些數據決定了RGW 在RADOS層的數據布局：當前5MB的RGW obj，不分part，分為2個stripe，第一個stripe 4194304（4MB），剩余1048576在第二個stripe，結束ofs為5242880。rules 中start_part_num=0 表示當前未分part。
看一個分part 上傳的manifest:

root@stor14 build]# bin/rados -c ceph.conf getxattr e34456f0-d371-4384-9007-70c60563fb0b.4848.1_20MB -p default.rgw.buckets.data user.rgw.manifest > /tmp/m
[root@stor14 build]# bin/ceph-dencoder type RGWObjManifest import /tmp/m decode dump_json
{
    "objs": [],
    "obj_size": 20971520,
    "explicit_objs": "false",
    "head_size": 0,
    "max_head_size": 0,
    "prefix": "20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx",
    "rules": [
        {
            "key": 0,
            "val": {
                "start_part_num": 1, # "When uploading a part, in addition to the upload ID, you must specify a part number. You can choose any part number between 1 and 10,000. A part number uniquely identifies a part and its position in the object you are uploading. "
                "start_ofs": 0,
                "part_size": 15728640,
                "stripe_max_size": 4194304,
                "override_prefix": ""
            }
        },
        {
            "key": 15728640,
            "val": {
                "start_part_num": 2,
                "start_ofs": 15728640,
                "part_size": 5242880,
                "stripe_max_size": 4194304,
                "override_prefix": ""
            }
        }
    ],
    "tail_instance": "",
    "tail_placement": {
        "bucket": {
            "name": "test2",
            "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
            "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
            "tenant": "",
            "explicit_placement": {
                "data_pool": "",
                "data_extra_pool": "",
                "index_pool": ""
            }
        },
        "placement_rule": "default-placement"
    },
    "begin_iter": {
        "part_ofs": 0,
        "stripe_ofs": 0,
        "ofs": 0,
        "stripe_size": 4194304,
        "cur_part_id": 1,
        "cur_stripe": 0,
        "cur_override_prefix": "",
        "location": {
            "placement_rule": "default-placement",
            "obj": {
                "bucket": {
                    "name": "test2",
                    "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "tenant": "",
                    "explicit_placement": {
                        "data_pool": "",
                        "data_extra_pool": "",
                        "index_pool": ""
                    }
                },
                "key": {
                    "name": "20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1", # first part key
                    "instance": "",
                    "ns": "multipart"  # tail 類型為multipart
                }
            },
            "raw_obj": {
                "pool": "",
                "oid": "",
                "loc": ""
            },
            "is_raw": false
        }
    },
    "end_iter": {
        "part_ofs": 20971520,
        "stripe_ofs": 20971520,
        "ofs": 20971520,
        "stripe_size": 4194304,
        "cur_part_id": 3, ###??
        "cur_stripe": 0,
        "cur_override_prefix": "",
        "location": {
            "placement_rule": "default-placement",
            "obj": {
                "bucket": {
                    "name": "test2",
                    "marker": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "bucket_id": "e34456f0-d371-4384-9007-70c60563fb0b.4848.1",
                    "tenant": "",
                    "explicit_placement": {
                        "data_pool": "",
                        "data_extra_pool": "",
                        "index_pool": ""
                    }
                },
                "key": {
                    "name": "20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.3", # last part key ,3 ??
                    "instance": "",
                    "ns": "multipart" # tail 類型為multipart
                }
            },
            "raw_obj": {
                "pool": "",
                "oid": "",
                "loc": ""
            },
            "is_raw": false
        }
    }
}

20MB大小的對象分為2個part 上傳。觀察manifest.rules，當前
key=0 part，也即第一個part，其start_part_num=1，part_size=15728640；
key=1 part，也即第二個part，其start_part_num=2，part_size=5242880，也即剩余大小；
AWS S3 要求multipart 時part number需要在1-1000間，不可以使用0。

ACL

[root@stor14 build]# bin/rados -c ceph.conf getxattr e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB -p default.rgw.buckets.data user.rgw.acl > /tmp/m
[root@stor14 build]# bin/ceph-dencoder type RGWAccessControlPolicy import /tmp/m decode dump_json
{
    "acl": {
        "acl_user_map": [
            {
                "user": "user1",
                "acl": 15
            }
        ],
        "acl_group_map": [],
        "grant_map": [
            {
                "id": "user1",
                "grant": {
                    "type": {
                        "type": 0
                    },
                    "id": "user1",
                    "email": "",
                    "permission": {
                        "flags": 15
                    },
                    "name": "user1",
                    "group": 0,
                    "url_spec": ""
                }
            }
        ]
    },
    "owner": {
        "id": "user1",
        "display_name": "user1"
    }
}

如果RGW 對象大小超過15MB, 利用s3cmd 上傳會自動分段上傳，也即multipart 上傳。

[root@stor14 build]# s3cmd put ./20MB s3://test2
upload: './20MB' -> 's3://test2/20MB'  [part 1 of 2, 15MB] [1 of 1]
 15728640 of 15728640   100% in    1s    11.65 MB/s  done
upload: './20MB' -> 's3://test2/20MB'  [part 2 of 2, 5MB] [1 of 1]
 5242880 of 5242880   100% in    0s     8.21 MB/s  done

[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.buckets.data
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_2
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_jcd1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2_1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_1
e34456f0-d371-4384-9007-70c60563fb0b.4281.15_dcj2
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_20MB
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_3
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2
e34456f0-d371-4384-9007-70c60563fb0b.4281.15_dcj1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_4MB
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_5MB
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_.lWnArC6BcKPkRjbGf-B0q23BSpxjql1_1
 
[root@stor14 build]# bin/rados -c ceph.conf ls -p default.rgw.buckets.data|grep 20MB
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_2
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2_1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1_20MB
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_3
e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2

這個20MB 的RGW 對象分成了7 個RADOS 對象，其中

head object：e34456f0-d371-4384-9007-70c60563fb0b.4848.1_20MB
tail objects：
- multipart obj：e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1
  - shadow objs：e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_1,
    e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_2,
    e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_3
- multipart obj：e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2
  - shadow objs：e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2_1

可以看到，multipart 上傳的對象會有一個head，默認每個part 15M，每個part 的第一個tail 為multipart obj，剩余都為shadow obj。
查看個rados 的大小：

[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1_20MB
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1_20MB mtime 2019-11-20 20:58:01.000000, size 0
head obj size 為0，multipart 情況head 只存元數據xattr
[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1 mtime 2019-11-20 20:58:00.000000, size 4194304
[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_1
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_1 mtime 2019-11-20 20:58:00.000000, size 4194304
[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_2
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_2 mtime 2019-11-20 20:58:00.000000, size 4194304
[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_3
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_3 mtime 2019-11-20 20:58:00.000000, size 3145728
[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2 mtime 2019-11-20 20:58:01.000000, size 4194304
[root@stor14 build]# bin/rados -c ceph.conf -p default.rgw.buckets.data stat e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2_1
default.rgw.buckets.data/e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2_1 mtime 2019-11-20 20:58:01.000000, size 1048576

0 + 4194304 + 4194304 + 4194304 + 3145728 + 4194304 + 1048576 = 20971520，正好是RGW obj "20MB"的大小。
一般的tail obj（shadow obj）中沒有元數據信息，不過multipart obj 會有一些元數據信息：

[root@stor14 build]# bin/rados -c ceph.conf listxattr e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_2 -p default.rgw.buckets.data

[root@stor14 build]# bin/rados -c ceph.conf listxattr e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1 -p default.rgw.buckets.data
user.rgw.acl
user.rgw.etag
user.rgw.pg_ver
user.rgw.source_zone
user.rgw.x-amz-content-sha256
user.rgw.x-amz-date

可以看到沒有manifest。
我們可以從multipart tail obj 中拿到和從head obj中一樣的acl 元數據。

[root@stor14 build]# bin/rados -c ceph.conf getxattr e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.2 -p default.rgw.buckets.data user.rgw.acl > /tmp/m
[root@stor14 build]# bin/ceph-dencoder type RGWAccessControlPolicy import /tmp/m decode dump_json
{
    "acl": {
        "acl_user_map": [
            {
                "user": "user1",
                "acl": 15
            }
        ],
        "acl_group_map": [],
        "grant_map": [
            {
                "id": "user1",
                "grant": {
                    "type": {
                        "type": 0
                    },
                    "id": "user1",
                    "email": "",
                    "permission": {
                        "flags": 15
                    },
                    "name": "user1",
                    "group": 0,
                    "url_spec": ""
                }
            }
        ]
    },
    "owner": {
        "id": "user1",
        "display_name": "user1"
    }
}

在未開啟versioning的情況下，RGW obj 對應的RADOS obj 的命名規則為

head： __<rgw_obj_name>，如 e34456f0-d371-4384-9007-70c60563fb0b.4848.1_20MB
（multipart上傳）mulpart tail: _ multipart<rgw_obj_name>.<manifest_prefix>.<part_id>，如 e34456f0-d371-4384-9007-70c60563fb0b.4848.1__multipart_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1
shadow tail：
- multipart 上傳： _ shadow<rgw_obj_name>.<manifest_prefix>.<part_id>_<stripe_id>，如 e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow_20MB.2~PDSpB4F7hIgKhjVwf6NqmJtBuKxm-mx.1_3
- 非multipart 上傳： _ shadow.<manifest_prefix> <stripe_id>，如 e34456f0-d371-4384-9007-70c60563fb0b.4848.1__shadow.lWnArC6BcKPkRjbGf-B0q23BSpxjql1_1

其中marker 就是bucket stats 中看到的marker，也是bucket id。

在開啟versioning 之后，會增加一個object_instance_id，這里暫不做詳細討論。

References

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