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Updated Erasure Coding for warm storage (markdown)

Chris Lu 2019-06-26 22:21:38 -07:00
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Erasure-Coding-for-warm-storage.md

@ -17,8 +17,8 @@ However, data can become warm or cold after a period of time. They are accessed
The downside:
* If some EC shards are missing, fetching data on those shards would be slower.
* Re-construct missing EC shards would require transmitting whole volume data.
* current EC volumes can not have blob deletion as of now. The blob deletion is working in progress.
* Compaction would require transmitting whole volume data.
* Only deletion is supported. Update is not supported.
* Compaction is WIP. This would require transmitting whole volume data.
## Architecture
SeaweedFS implemented 10.4 Reed-Soloman Erasure Coding (EC). The large volumes are split into chunks of 1GB, and every 10 data chunks are also encoded into 4 parity chunks. So a 30 GB data volume will be encoded into 14 EC shards, each shard is of size 3 GB and has 3 EC blocks.