Sorry, I have not measure it. But I think it should really reduce latency when hit miss in cache pool and do_proxy_read.
2015-03-17 16:39 GMT+08:00 Loic Dachary <[email protected]>: > > > 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 <[email protected]>: >>> >>> >>> On 17/03/2015 08:52, Xinze Chi wrote: >>>> ---------- Forwarded message ---------- >>>> From: Xinze Chi <[email protected]> >>>> Date: 2015-03-17 15:52 GMT+08:00 >>>> Subject: Re: Fwd: Reduce read latency and bandwidth for ec pool >>>> To: Loic Dachary <[email protected]> >>>> >>>> >>>> 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 <[email protected]>: >>>>> 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 [email protected] >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> >>> >>> -- >>> Loïc Dachary, Artisan Logiciel Libre >>> > > -- > Loïc Dachary, Artisan Logiciel Libre > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
