NewStore (new osd backend) » History » Version 1
Jessica Mack, 07/10/2015 09:32 PM
| 1 | 1 | Jessica Mack | h1. NewStore (new osd backend) |
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| 3 | h3. Summary |
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| 5 | Create a replacement for FileStore that implements the ObjectStore API. |
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| 6 | The goal is to be |
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| 7 | * general purpose (HDD or SSD) |
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| 8 | * avoid double-writes for new objects and sequential writes |
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| 9 | * be more efficient about small writes |
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| 10 | * leverage a key/value database for our metadata |
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| 11 | * leverage a POSIX file system to block management of object data |
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| 13 | h3. Owners |
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| 15 | * Sage Weil (Red Hat) |
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| 16 | * Name (Affiliation) |
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| 17 | * Name |
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| 19 | h3. Interested Parties |
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| 21 | * Guang Yang (Yahoo!) |
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| 22 | * Name (Affiliation) |
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| 23 | * Name |
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| 25 | h3. Current Status |
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| 27 | There is a work-in-progress implementation available at https://github.com/liewegas/ceph/commits/wip-newstore |
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| 29 | h3. Detailed Description |
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| 31 | There is a reasonable summary of the current state of things at: http://marc.info/?l=ceph-devel&m=142438985013041&w=2 |
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| 32 | The goal is to get a working prototype available as soon as possible with some basic infrastructure for atomic updates and so forth. We can iterate on how to be extra clever after that. |
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| 34 | h3. Work items |
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| 36 | h4. Coding tasks |
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| 38 | # get wip-temp merged; this simplifies our usage of the collections so that there is 1 per PG and no cross-collection moves or renames. 'temp' becomes a special class of objects within a collection with some special semantics (they disappear on restart). there is also a bunch of other cleanup in this branch. |
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| 39 | # get NewStore write-ahead-log infrastructure working |
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| 40 | # mangle DBObjectMap so that we can use it while embedding the head into the onode_t. possiblye rewrite/steal from this as the design shoudl be revisited. |
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| 41 | # at this point NewStore should be functional and pass tests |
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| 42 | # make the write path do the fsync and transaction completion asynchrnoously |
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| 43 | # use AIO + DIO for writes when WONTNEED; use buffered writes otherwise |
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| 44 | # make a smart fsyncer (many threads to improve concurrency, or leverage parallel aio_fsync if we can) |
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| 45 | # test to ensure it is power-fail safe. |
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| 46 | # add open-by-handle support (i.e., avoid path lookup overhead) |
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| 47 | # consider writing some small writes into the kv store instead of taking the WAL path and applying them to the file |