Re: Fwd: Reduce read latency and bandwidth for ec pool

[Loic Dachary <loic@dachary.org>]

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Hi,

On 17/03/2015 08:27, Xinze Chi wrote:
> hi, loic:
> 
>    I have an idea which could reduce read latency and bandwidth for ec pool.
> 
>    But, I don't know whether it is feasible.
> 
>    Such as ec pool stripe_width = 16384 = 4 * 4096,  K = 4, M =2
> 
>    So ceph will partition the total of 16384 bytes to 4 data chunk,
> and encoding 2 parity chunk
> 
>    shard_0 include 0 - (4096-1) in original data;
>    shard_1 include 4096 - (4096*2 - 1) in original data;
>    shard_2 include 4096*2 - (4096 * 3 -1) in original data;
>    shard_3 include 4096*3 - (4096 * 4 - 1) in original data
>    shard_4 include parity chunk
>    shard_5 include parity chunk
> 
>     Now if client read (offset 0, len 4096) from object, it should
> read 4 shard (from 0-3) and decode all this 4 chunk.
> 
>     But, this example, maybe we can compute the destination shard
> based on ec pool config ,read offset and read len , we only read
> 
> shard_0 and return it to client, because shard_0 has include all data
> as client need.

That optimization makes sense to me. I guess you're interested in having small objects in the pool and only read a few bytes at a time ?

Cheers

> 
>     Wait for your comment.
> 
>     Thanks.
> 

-- 
Loïc Dachary, Artisan Logiciel Libre


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