On 17/03/2015 09:45, Xinze Chi wrote: > Sorry, I have not measure it. > > But I think it should really reduce latency when hit miss in cache > pool and do_proxy_read. Interesting. I bet Jason or Josh have an opinion about this. Cheers > > 2015-03-17 16:39 GMT+08:00 Loic Dachary <loic@xxxxxxxxxxx>: >> >> >> 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 >> -- Loïc Dachary, Artisan Logiciel Libre
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