Feature #12316: For EC pool, read K+M shards (instead of K) to reduce latency (with IO overhead) - Ceph - Ceph

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Feature #12316

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For EC pool, read K+M shards (instead of K) to reduce latency (with IO overhead)

Added by Guang Yang almost 9 years ago. Updated over 8 years ago.

Status:

Resolved

Priority:

Normal

Assignee:

Guang Yang

Category:

OSD

Target version:

% Done:

Source:

Community (dev)

Tags:

Backport:

Reviewed:

Affected Versions:

Pull request ID:

Description

EC pool has a large fan outs (K) for reading, which means, the latency of the client requests depends on the slowest shard of the K sub-read requests, this feature tries to optimize for performance with I/O overhead, basically, we try to issue K+M sub-read requests and use the first K response to serve the client request, to avoid the impact of the slowest M sub-read requests.

As discussed with Sam, we want to do in the following way:
1> Add a pool setting to turn the feature on and off
2> Do the request on per OP basis, that is, for each request, it hints to the PGBackend to use this feature or not.