原文见于：http://swift.openstack.org/overview_architecture.html
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Swift Architectural Overview
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.. TODO - add links to more detailed overview in each section below.
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Proxy Server
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The Proxy Server is responsible for tying together the rest of the Swift
architecture. For each request, it will look up the location of the account,
container, or object in the ring (see below) and route the request accordingly.
The public API is also exposed through the Proxy Server.
Proxy Server负责将Swift架构的其他部分绑定在一起。对每一个请求，Proxy Server都要在环中查找account,container,或者object的位置，
并且将请求转送到对应的地方。公开的API也是通过Proxy Server暴露出来。
A large number of failures are also handled in the Proxy Server. For
example, if a server is unavailable for an object PUT, it will ask the
ring for a handoff server and route there instead.
大量的失败也是由Proxy Server处理的。比如，如果一个server无法对一个object的PUT操作进行相应，它将从环中查询一个可以接手的server并将请求转递给它。
When objects are streamed to or from an object server, they are streamed
directly through the proxy server to of from the user -- the proxy server
does not spool them.
当objects被传送object server或者从object server下载，他们将被直接通过proxy server传送----proxy server不回对他们进行“假脱机”。
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The Ring
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A ring represents a mapping between the names of entities stored on disk and
their physical location. There are separate rings for accounts, containers, and
objects. When other components need to perform any operation on an object,
container, or account, they need to interact with the appropriate ring to
determine its location in the cluster.
环代表磁盘上所存储的实体的名称与他们物理位置之间的映射。它们是分别对应于accounts,containers和objects的环。
当其它的组件需要对object,container或者account执行某个操作时，它们需要通过与对应的环沟通来确定执行客体在集群中的位置。
The Ring maintains this mapping using zones, devices, partitions, and replicas.
Each partition in the ring is replicated, by default, 3 times accross the
cluster, and the locations for a partition are stored in the mapping maintained
by the ring. The ring is also responsible for determining which devices are
used for handoff in failure scenarios.
环通过zones（区域）,devices（存储）,partitions（分区）和replicas（副本）来维护这些映射。
环中的每个分区都会被在集群中（还是集群间？）备份（默认3份），并且每个分区的位置信息将存储在环所维护的映射中。
环同时也负责确定由哪个device（存储）来接手那些失败的操作。
Data can be isolated with the concept of zones in the ring. Each replica
of a partition is guaranteed to reside in a different zone. A zone could
represent a drive, a server, a cabinet, a switch, or even a datacenter.
数据可以通过环中的区域这个概念来实现隔离。每个分区的备份都会被保证存储在不同的区域中.
一个区域可以代表一个存储,一个服务器,一个机柜，一个交换机，甚至一个数据中心。
The partitions of the ring are equally divided among all the devices in the
Swift installation. When partitions need to be moved around (for example if a
device is added to the cluster), the ring ensures that a minimum number of
partitions are moved at a time, and only one replica of a partition is moved at
a time.
环的分区是对swift装置中所有存储设备的平均划分来确定的。当分区需要被移动（比如，一个新的存储设备加入此集群），
环将确保每次只有最小数量的分区会被移动，并且每次只有一个分区的备份会被移动。
Weights can be used to balance the distribution of partitions on drives
across the cluster. This can be useful, for example, when different sized
drives are used in a cluster.
权重可以用来均衡存储设备上的分区在集群间的分布。这是非常有用的，比如，当大小不同的存储设备被使用在同一集群中时。
The ring is used by the Proxy server and several background processes
(like replication).
环被Proxy和一些后台进程所使用（例如复制进程）
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Object Server
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The Object Server is a very simple blob storage server that can store,
retrieve and delete objects stored on local devices. Objects are stored
as binary files on the filesystem with metadata stored in the file's
extended attributes (xattrs). This requires that the underlying filesystem
choice for object servers support xattrs on files. Some filesystems,
like ext3, have xattrs turned off by default.
Object Server是一个非常简单的块存储服务器，它可以用来存储，获取和删除存储在本地存储设备上的objects。
objects以二进制文件的形式，连带着存储在扩展属性（xattrs）中的元数据，被存储在文件系统上（xattrs）。
这需要存储objects的基础文件系统支持文件的xattrs。像ext3的一些文件系统，默然是关闭xattrs的。
Each object is stored using a path derived from the object name's hash and
the operation's timestamp. Last write always wins, and ensures that the
latest object version will be served. A deletion is also treated as a
version of the file (a 0 byte file ending with ".ts", which stands for
tombstone). This ensures that deleted files are replicated correctly and
older versions don't magically reappear due to failure scenarios.
每个object是通过从“object名的哈希和操作发生的时间戳”生成的path来存储的。最后一次的写入总是赢家，并且确保最新版本的object被服务。
一个删除操作也被视为目标文件的一个版本（一个0字节大小并且名称以.ts结尾的文件，其代表此文件的墓碑）。
这将确保所有副本都会被正确删除，并且旧的版本不会因为失败的操作而诡异地重新出现。
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Container Server
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The Container Server's primary job is to handle listings of objects. It
doesn't know where those object's are, just what objects are in a specific
container. The listings are stored as sqlite database files, and replicated
across the cluster similar to how objects are. Statistics are also tracked
that include the total number of objects, and total storage usage for that
container.
Container Server的主要职责是提供objects的列表。它不知道这些objects被存储在何处，只知道哪些objcts是归属于某一指定的容器中。
objects列表以sqlite数据库文件的形式存储，并且像objects那样在集群中被备份。包含obejcts总数量和容器已用容量的信息也将被追踪统计。
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Account Server
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The Account Server is very similar to the Container Server, excepting that
it is responsible for listings of containers rather than objects.
Account Server与Container Server非常类似，唯一不同的在于，account server是用来列举containers清单的，而非objects清单。
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Replication
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Replication is designed to keep the system in a consistent state in the face
of temporary error conditions like network outages or drive failures.
复制器被设计用来在面临临时性错误（比如断网或存储器错误）时，保护系统的一致性。
The replication processes compare local data with each remote copy to ensure
they all contain the latest version. Object replication uses a hash list to
quickly compare subsections of each partition, and container and account
replication use a combination of hashes and shared high water marks.
复制进程通过将本地数据与每一个远程备份进行比较，来确保它们都是最新版本的数据。
Object复制器使用一个哈希列表来迅速地比较每一个分区的子部分，同时container和account复制器使用哈希的排列并且共享高峰标记。
Replication updates are push based. For object replication, updating is
just a matter of rsyncing files to the peer. Account and container
replication push missing records over HTTP or rsync whole database files.
复制操作的更新是基于PUSH的方式。比如object的复制操作，更新就是一个往其他节点同步文件的过程。
Account和container的复制操作通过HTTP来PUSH丢失的记录,或着远程同步全部的数据库文件。
The replicator also ensures that data is removed from the system. When an
item (object, container, or account) is deleted, a tombstone is set as the
latest version of the item. The replicator will see the tombstone and ensure
that the item is removed from the entire system.
复制器同时也确保数据从系统的删除。当一个条目(object, container, account)被删除，
一个墓碑将作为此目标的最新版本被设置。复制器将见到此墓碑，并将确保此目标被从所有的系统中删除。
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Updaters
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There are times when container or account data can not be immediately
updated. This usually occurs during failure scenarios or periods of high
load. If an update fails, the update is queued locally on the filesystem,
and the updater will process the failed updates. This is where an eventual
consistency window will most likely come in to play. For example, suppose a
container server is under load and a new object is put in to the system. The
object will be immediately available for reads as soon as the proxy server
responds to the client with success. However, the container server did not
update the object listing, and so the update would be queued for a later
update. Container listings, therefore, may not immediately contain the object.
当contaniner或account数据不能被立即更新的情况会多次出现。这通常当出现错误或者系统过载时会发生。
当一个更新失败时，更新操作就会在本地文件系统上排队，然后更新器会处理这些失败的更新。这时最终一致性的窗口会适时地出现。
比如，假设当一个container server处于低负载并且一个新的object被put到系统中时，一旦proxy server向客户端回复成功消息，
此object就将立即可读。然而，container server不会更新object的列表，并且因此更新将被排队以等待稍候的更新。
此刻container列举的清单，可能不回立马包含此object。
In practice, the consistency window is only as large as the frequency at
which the updater runs and may not even be noticed as the proxy server will
route listing requests to the first container server which responds. The
server under load may not be the one that serves subsequent listing
requests -- one of the other two replicas may handle the listing.
在实践中，一致性窗口的大小仅仅与更新器运行的频率一致，并且Proxy Server不会将list请求转递给最初对请求进行回复的那个Container Server。
低负载的服务器可能不会接手接下来的list请求---其他的两个备份中的一个会处理此list请求。
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Auditors
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Auditors crawl the local server checking the integrity of the objects,
containers, and accounts. If corruption is found (in the case of bit rot,
for example), the file is quarantined, and replication will replace the bad
file from another replica. If other errors are found they are logged (for
example, an object's listing can't be found on any container server it
should be).
审计师爬行本地服务器来检查objects,containers和accounts的完整性。
当一个文件被发现有损坏（比如一点损坏），它将被隔离，并且复制器将同其他的副本复制一份来代替此损坏的文件。
如果有别的错误发生，它们将被记录日志（比如列举一个object时，在所有的它应该位于的container server中都无法找到）
