docs: curvefs space design #959
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aspirer
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Jan 10, 2022
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| ## 后续版本需要解决的问题 | ||
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| - [ ] 空间分配信息如何重建 |
aspirer
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Jan 10, 2022
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| 之前剩余的 30MiB ~ 2MiB 的 extent 完全分配出去，所以从 level2 中的 list 中删除。 | ||
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| 文件 inode 中的 extent 可以将两次的申请结果进行合并，得到（0，28MiB，4MiB）。 |
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合并extent逻辑是在更新space信息的时候同步做的还是后台异步做的？
aspirer
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Jan 10, 2022
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| 为了避免整个问题，可以将整个空间，由多个分配器来进行管理，每个分配器管理不同的地址空间。比如，将整个空间划分为 10 组，每组空间都有一个空间分配器进行管理。 | ||
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| 在申请空间时，如果没有附带期望地址空间的 offset，则随机选取一个分配器进行空间分配。如果附带了期望的 offset，则由对应的分配器进行处理。 |
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如果对应offset的分配器进程异常怎么处理？降级到没有指定offset的逻辑？什么时候恢复正常的逻辑？等进程启动？另外如果要扩容bs卷，或者继续细分地址空间怎么处理？
aspirer
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Jan 10, 2022
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| 在线扩容时，直接在新扩容的空间上，创建新的空间分配器进行空间管理。 | ||
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| 文件系统重新加载时，再将所有的空间，按照上述的策略，进行分组管理。 |
aspirer
reviewed
Jan 10, 2022
| - [ ] 空间分配信息如何重建 | ||
| - [ ] 高可用 | ||
| - [ ] 幂等请求处理 | ||
| - [ ] PB 级别情况下的性能 |
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其实我一直有个疑问，我们bs卷要支持单卷PB级容量，是否需要做一些改动？或者说优化？
目前云盘场景下，单卷都是TB级别。如何验证单卷支持PB级别甚至几十PB都是没问题的？
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另外是否可以考虑下，当前的设计方案最有可能成为性能瓶颈的点在哪？也列一些，为方案实现做参考，预埋一些metric或者写代码的时候可以多留点冗余？
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introduce curvefs space design