前一段时间看了Ceph的论文，有看到很多介绍用Openstack+Ceph搭建私有云的方案。自然想了解一下Ceph和Swift什么关系。这篇博客应该是Swift开发者2013年写的：Ceph and Swift: Why we are not fighting. 应该是解释的最清楚的。

开篇就是要回答的问题：

While chatting with different people there was a recurrent question coming up to me: people wanted to know whether “Ceph is better than Swift”.他的回复就是：But Ceph and Swift are not actually competing with each other: they are two different technologies, each with a different purpose. There is some feature overlap between both but the two have different use-cases and can actually live happily together in the same deployment.

首先特征对比：

CephStarted in 2006Written in C++.Strongly consistent.Block storage.Object storage.Ceph is doing a lot of more than just object storage. Using it as an Open Source block storage (a way to provide remote virtual disks) is what people would start to get attracted by. It does this brilliantly since it seems to become a very popular block storage system option for OpenStack deployments and that’s a win for OpenStack and the Open Source community in general.

Swift

Started in 2008Written in Python.Eventually consistent.Object storage.Swift, on the other hand, does one thing and does it well. Its only ambition is to do object storage and provide a REST api to access it. It is eventually consistent. This means that when hardware fails (which is inevitable in a cluster) Swift will fall back to providing high availability to the data. Swift’s eventual consistency window is most likely to be seen when reading objects that were overwritten while hardware has failed and when looking at container listings when many objects in that container are created at the same time.

然后是应用场景

If you had to choose only one and you had a requirement for block storage you definitely want to go with CEPH. If you had only a object storage use case then I would advise you to go with Swift.

最后是结论：

Don’t think of Swift and Ceph as rivals. Both are great OpenSource projects with a specific set of tasks in mind. The main competition are proprietary software solutions resulting in a vendor lock-in, and both Swift and Ceph, with their strong communities and lively discussions, are great solutions for a vast majority of challenges.

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