On 17/03/2015 09:05, Xinze Chi wrote: > RBD. Did you measure that RBD does a significant amount of reads that would be optimized in this way ? > Maybe we could use tier pool. > > Thanks > > 2015-03-17 16:02 GMT+08:00 Loic Dachary <loic@xxxxxxxxxxx>: >> >> >> On 17/03/2015 08:52, Xinze Chi wrote: >>> ---------- Forwarded message ---------- >>> From: Xinze Chi <xmdxcxz@xxxxxxxxx> >>> Date: 2015-03-17 15:52 GMT+08:00 >>> Subject: Re: Fwd: Reduce read latency and bandwidth for ec pool >>> To: Loic Dachary <loic@xxxxxxxxxxx> >>> >>> >>> Yes, In my VDI environment, client read 4k every time. If we can read >>> object from only shard. It would reduce the latency and bandwidth a >>> lot. >> >> I'm curious about your workload. Are you using RadosGW ? RBD ? >> >>> Thanks. >>> >>> 2015-03-17 15:48 GMT+08:00 Loic Dachary <loic@xxxxxxxxxxx>: >>>> 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 >>>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> >> >> -- >> Loïc Dachary, Artisan Logiciel Libre >> -- Loïc Dachary, Artisan Logiciel Libre
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