On Fri, 10 Apr 2015, Ning Yao wrote: > KV store introduces too much write amplification, we may need > self-implemented WAL? What we really want is to hint to the kv store that these keys (or this key range) is short-lived and should never get compacted. And/or, we need to just make sure the wal is sufficiently large so that in practice that never happens to those keys. Putting them outside the kv store means an additional seek/sync for disks, which defeats most of the purpose. Maybe it makes sense for flash... but the above avoids the problem in either case. I think we should target rocksdb for our initial tuning attempts. So far all I've done is played a bit with the file size (1mb -> 4mb -> 8mb) but my ad hoc tests didn't see much difference. sage > Regards > Ning Yao > > > 2015-04-10 14:11 GMT+08:00 Duan, Jiangang <jiangang.duan@xxxxxxxxx>: > > IMHO, the newstore performance depends so much on KV store performance due to the WAL - so pick up the right KV or tune it will be the 1st step to do. > > > > -jiangang > > > > > > -----Original Message----- > > From: ceph-devel-owner@xxxxxxxxxxxxxxx [mailto:ceph-devel-owner@xxxxxxxxxxxxxxx] On Behalf Of Mark Nelson > > Sent: Friday, April 10, 2015 1:01 AM > > To: Sage Weil > > Cc: ceph-devel > > Subject: Re: Initial newstore vs filestore results > > > > On 04/08/2015 10:19 PM, Mark Nelson wrote: > >> On 04/07/2015 09:58 PM, Sage Weil wrote: > >>> What would be very interesting would be to see the 4KB performance > >>> with the defaults (newstore overlay max = 32) vs overlays disabled > >>> (newstore overlay max = 0) and see if/how much it is helping. > >> > >> And here we go. 1 OSD, 1X replication. 16GB RBD volume. > >> > >> 4MB write read randw randr > >> default overlay 36.13 106.61 34.49 92.69 > >> no overlay 36.29 105.61 34.49 93.55 > >> > >> 128KB write read randw randr > >> default overlay 1.71 97.90 1.65 25.79 > >> no overlay 1.72 97.80 1.66 25.78 > >> > >> 4KB write read randw randr > >> default overlay 0.40 61.88 1.29 1.11 > >> no overlay 0.05 61.26 0.05 1.10 > >> > > > > Update this morning. Also ran filestore tests for comparison. Next we'll look at how tweaking the overlay for different IO sizes affects things. IE the overlay threshold is 64k right now and it appears that 128K write IOs for instance are quite a bit worse with newstore currently than with filestore. Sage also just committed changes that will allow overlay writes during append/create which may help improve small IO write performance as well in some cases. > > > > 4MB write read randw randr > > default overlay 36.13 106.61 34.49 92.69 > > no overlay 36.29 105.61 34.49 93.55 > > filestore 36.17 84.59 34.11 79.85 > > > > 128KB write read randw randr > > default overlay 1.71 97.90 1.65 25.79 > > no overlay 1.72 97.80 1.66 25.78 > > filestore 27.15 79.91 8.77 19.00 > > > > 4KB write read randw randr > > default overlay 0.40 61.88 1.29 1.11 > > no overlay 0.05 61.26 0.05 1.10 > > filestore 4.14 56.30 0.42 0.76 > > > > Seekwatcher movies and graphs available here: > > > > http://nhm.ceph.com/newstore/20150408/ > > > > Note for instance the very interesting blktrace patterns for 4K random writes on the OSD in each case: > > > > http://nhm.ceph.com/newstore/20150408/filestore/RBD_00004096_randwrite.png > > http://nhm.ceph.com/newstore/20150408/default_overlay/RBD_00004096_randwrite.png > > http://nhm.ceph.com/newstore/20150408/no_overlay/RBD_00004096_randwrite.png > > > > Mark > > -- > > 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 > > -- > > 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 > > -- 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
