Which iodepth did you use for those benchs? > I really don't understand why I can't get more rand read iops with 4K block ... Me neither, hope to get some clarification from the Inktank guys. It doesn't make any sense to me... -- Bien cordialement. Sébastien HAN. On Mon, Nov 19, 2012 at 8:11 PM, Alexandre DERUMIER <aderumier@xxxxxxxxx> wrote: >>>@Alexandre: is it the same for you? or do you always get more IOPS with seq? > > rand read 4K : 6000 iops > seq read 4K : 3500 iops > seq read 4M : 31iops (1gigabit client bandwith limit) > > rand write 4k: 6000iops (tmpfs journal) > seq write 4k: 1600iops > seq write 4M : 31iops (1gigabit client bandwith limit) > > > I really don't understand why I can't get more rand read iops with 4K block ... > > I try with high end cpu for client, it doesn't change nothing. > But test cluster use old 8 cores E5420 @ 2.50GHZ (But cpu is around 15% on cluster during read bench) > > > ----- Mail original ----- > > De: "Sébastien Han" <han.sebastien@xxxxxxxxx> > À: "Mark Kampe" <mark.kampe@xxxxxxxxxxx> > Cc: "Alexandre DERUMIER" <aderumier@xxxxxxxxx>, "ceph-devel" <ceph-devel@xxxxxxxxxxxxxxx> > Envoyé: Lundi 19 Novembre 2012 19:03:40 > Objet: Re: RBD fio Performance concerns > > @Sage, thanks for the info :) > @Mark: > >> If you want to do sequential I/O, you should do it buffered >> (so that the writes can be aggregated) or with a 4M block size >> (very efficient and avoiding object serialization). > > The original benchmark has been performed with 4M block size. And as > you can see I still get more IOPS with rand than seq... I just tried > with 4M without direct I/O, still the same. I can print fio results if > it's needed. > >> We do direct writes for benchmarking, not because it is a reasonable >> way to do I/O, but because it bypasses the buffer cache and enables >> us to directly measure cluster I/O throughput (which is what we are >> trying to optimize). Applications should usually do buffered I/O, >> to get the (very significant) benefits of caching and write aggregation. > > I know why I use direct I/O. It's synthetic benchmarks, it's far away > from a real life scenario and how common applications works. I just > try to see the maximum I/O throughput that I can get from my RBD. All > my applications use buffered I/O. > > @Alexandre: is it the same for you? or do you always get more IOPS with seq? > > Thanks to all of you.. > > > On Mon, Nov 19, 2012 at 5:54 PM, Mark Kampe <mark.kampe@xxxxxxxxxxx> wrote: >> Recall: >> 1. RBD volumes are striped (4M wide) across RADOS objects >> 2. distinct writes to a single RADOS object are serialized >> >> Your sequential 4K writes are direct, depth=256, so there are >> (at all times) 256 writes queued to the same object. All of >> your writes are waiting through a very long line, which is adding >> horrendous latency. >> >> If you want to do sequential I/O, you should do it buffered >> (so that the writes can be aggregated) or with a 4M block size >> (very efficient and avoiding object serialization). >> >> We do direct writes for benchmarking, not because it is a reasonable >> way to do I/O, but because it bypasses the buffer cache and enables >> us to directly measure cluster I/O throughput (which is what we are >> trying to optimize). Applications should usually do buffered I/O, >> to get the (very significant) benefits of caching and write aggregation. >> >> >>> That's correct for some of the benchmarks. However even with 4K for >>> seq, I still get less IOPS. See below my last fio: >>> >>> # fio rbd-bench.fio >>> seq-read: (g=0): rw=read, bs=4K-4K/4K-4K, ioengine=libaio, iodepth=256 >>> rand-read: (g=1): rw=randread, bs=4K-4K/4K-4K, ioengine=libaio, >>> iodepth=256 >>> seq-write: (g=2): rw=write, bs=4K-4K/4K-4K, ioengine=libaio, iodepth=256 >>> rand-write: (g=3): rw=randwrite, bs=4K-4K/4K-4K, ioengine=libaio, >>> iodepth=256 >>> fio 1.59 >>> Starting 4 processes >>> Jobs: 1 (f=1): [___w] [57.6% done] [0K/405K /s] [0 /99 iops] [eta >>> 02m:59s] >>> seq-read: (groupid=0, jobs=1): err= 0: pid=15096 >>> read : io=801892KB, bw=13353KB/s, iops=3338 , runt= 60053msec >>> slat (usec): min=8 , max=45921 , avg=296.69, stdev=1584.90 >>> clat (msec): min=18 , max=133 , avg=76.37, stdev=16.63 >>> lat (msec): min=18 , max=133 , avg=76.67, stdev=16.62 >>> bw (KB/s) : min= 0, max=14406, per=31.89%, avg=4258.24, >>> stdev=6239.06 >>> cpu : usr=0.87%, sys=5.57%, ctx=165281, majf=0, minf=279 >>> IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >>> >=64=100.0% >>> submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.0% >>> complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.1% >>> issued r/w/d: total=200473/0/0, short=0/0/0 >>> >>> lat (msec): 20=0.01%, 50=9.46%, 100=90.45%, 250=0.10% >>> rand-read: (groupid=1, jobs=1): err= 0: pid=16846 >>> read : io=6376.4MB, bw=108814KB/s, iops=27203 , runt= 60005msec >>> slat (usec): min=8 , max=12723 , avg=33.54, stdev=59.87 >>> clat (usec): min=4642 , max=55760 , avg=9374.10, stdev=970.40 >>> lat (usec): min=4671 , max=55788 , avg=9408.00, stdev=971.21 >>> bw (KB/s) : min=105496, max=109136, per=100.00%, avg=108815.48, >>> stdev=648.62 >>> cpu : usr=8.26%, sys=49.11%, ctx=1486259, majf=0, minf=278 >>> IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >>> >=64=100.0% >>> submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.0% >>> complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.1% >>> issued r/w/d: total=1632349/0/0, short=0/0/0 >>> >>> lat (msec): 10=83.39%, 20=16.56%, 50=0.04%, 100=0.01% >>> seq-write: (groupid=2, jobs=1): err= 0: pid=18653 >>> write: io=44684KB, bw=753502 B/s, iops=183 , runt= 60725msec >>> slat (usec): min=8 , max=1246.8K, avg=5402.76, stdev=40024.97 >>> clat (msec): min=25 , max=4868 , avg=1384.22, stdev=470.19 >>> lat (msec): min=25 , max=4868 , avg=1389.62, stdev=470.17 >>> bw (KB/s) : min= 7, max= 2165, per=104.03%, avg=764.65, >>> stdev=353.97 >>> cpu : usr=0.05%, sys=0.35%, ctx=5478, majf=0, minf=21 >>> IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.3%, >>> >=64=99.4% >>> submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.0% >>> complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.1% >>> issued r/w/d: total=0/11171/0, short=0/0/0 >>> >>> lat (msec): 50=0.21%, 100=0.44%, 250=0.97%, 500=1.49%, 750=4.60% >>> lat (msec): 1000=12.73%, 2000=66.36%, >=2000=13.20% >>> rand-write: (groupid=3, jobs=1): err= 0: pid=20446 >>> write: io=208588KB, bw=3429.5KB/s, iops=857 , runt= 60822msec >>> slat (usec): min=10 , max=1693.9K, avg=1148.15, stdev=15210.37 >>> clat (msec): min=22 , max=5639 , avg=297.37, stdev=430.27 >>> lat (msec): min=22 , max=5639 , avg=298.52, stdev=430.84 >>> bw (KB/s) : min= 0, max= 7728, per=31.44%, avg=1078.21, >>> stdev=2000.45 >>> cpu : usr=0.34%, sys=1.61%, ctx=37183, majf=0, minf=19 >>> IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >>> >=64=99.9% >>> submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.0% >>> complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >>> >=64=0.1% >>> issued r/w/d: total=0/52147/0, short=0/0/0 >>> >>> lat (msec): 50=2.82%, 100=25.63%, 250=46.12%, 500=10.36%, 750=5.10% >>> lat (msec): 1000=2.91%, 2000=5.75%, >=2000=1.33% >>> >>> Run status group 0 (all jobs): >>> READ: io=801892KB, aggrb=13353KB/s, minb=13673KB/s, maxb=13673KB/s, >>> mint=60053msec, maxt=60053msec >>> >>> Run status group 1 (all jobs): >>> READ: io=6376.4MB, aggrb=108814KB/s, minb=111425KB/s, >>> maxb=111425KB/s, mint=60005msec, maxt=60005msec >>> >>> Run status group 2 (all jobs): >>> WRITE: io=44684KB, aggrb=735KB/s, minb=753KB/s, maxb=753KB/s, >>> mint=60725msec, maxt=60725msec >>> >>> Run status group 3 (all jobs): >>> WRITE: io=208588KB, aggrb=3429KB/s, minb=3511KB/s, maxb=3511KB/s, >>> mint=60822msec, maxt=60822msec >>> >>> Disk stats (read/write): >>> rbd1: ios=1832984/63270, merge=0/0, ticks=16374236/17012132, >>> in_queue=33434120, util=99.79% -- 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
