I think with the command
dd of=/dev/zero
you are probably measuring write performance of /dev/zero. You should use of=/dev/null for dropping IO.
=================
Frank Schilder
AIT Risø Campus
Bygning 109, rum S14
________________________________________
From: linghucongsong <linghucongsong@xxxxxxx>
Sent: 27 August 2019 16:59:18
To: jesper@xxxxxxxx
Cc: ceph-users@xxxxxxx
Subject: Re: the ceph rbd read dd with fio performance diffrent so huge?
Thank you for reply.
dd read is 410KB/s。 fio read is 991.23MB/s .
dd*30 410KB*30/1024 =12MB is also so huge diffrent with the fio 991.23MB/s .
At 2019-08-27 22:31:51, jesper@xxxxxxxx wrote:
concurrency is widely different 1:30
Jesper
Sent from myMail for iOS
Tuesday, 27 August 2019, 16.25 +0200 from linghucongsong@xxxxxxx <linghucongsong@xxxxxxx>:
The performance with the dd and fio diffrent is so huge?
I have 25 OSDS with 8TB hdd. with dd I only get 410KB/s read perfomance,but with fio I get 991.23MB/s read perfomance.
like below:
Thanks in advance!
root@Server-d5754749-cded-4964-8129-ba1accbe86b3:~# time dd of=/dev/zero if=/mnt/testw.dbf bs=4k count=10000 iflag=direct
10000+0 records in
10000+0 records out
40960000 bytes (41 MB, 39 MiB) copied, 99.9445 s, 410 kB/s
real 1m39.950s
user 0m0.040s
sys 0m0.292s
root@Server-d5754749-cded-4964-8129-ba1accbe86b3:~# fio --filename=/mnt/test1 -direct=1 -iodepth 1 -thread -rw=read -ioengine=libaio -bs=4k -size=1G -numjobs=30 -runtime=10 -group_reporting -name=mytest
mytest: (g=0): rw=read, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio, iodepth=1
...
fio-2.2.10
Starting 30 threads
Jobs: 30 (f=30): [R(30)] [100.0% done] [1149MB/0KB/0KB /s] [294K/0/0 iops] [eta 00m:00s]
mytest: (groupid=0, jobs=30): err= 0: pid=5261: Tue Aug 27 13:37:28 2019
read : io=9915.2MB, bw=991.23MB/s, iops=253752, runt= 10003msec
slat (usec): min=2, max=200020, avg=39.10, stdev=1454.14
clat (usec): min=1, max=160019, avg=38.57, stdev=1006.99
lat (usec): min=4, max=200022, avg=87.37, stdev=1910.99
clat percentiles (usec):
| 1.00th=[ 1], 5.00th=[ 1], 10.00th=[ 1], 20.00th=[ 1],
| 30.00th=[ 1], 40.00th=[ 1], 50.00th=[ 1], 60.00th=[ 1],
| 70.00th=[ 1], 80.00th=[ 2], 90.00th=[ 2], 95.00th=[ 2],
| 99.00th=[ 612], 99.50th=[ 684], 99.90th=[ 780], 99.95th=[ 1020],
| 99.99th=[56064]
bw (KB /s): min= 7168, max=46680, per=3.30%, avg=33460.79, stdev=12024.35
lat (usec) : 2=73.62%, 4=22.38%, 10=0.05%, 20=0.03%, 50=0.01%
lat (usec) : 100=0.01%, 250=0.03%, 500=1.93%, 750=1.75%, 1000=0.14%
lat (msec) : 2=0.01%, 4=0.01%, 10=0.01%, 20=0.01%, 50=0.01%
lat (msec) : 100=0.03%, 250=0.01%
cpu : usr=1.83%, sys=4.30%, ctx=104743, majf=0, minf=59
IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
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=0.0%
issued : total=r=2538284/w=0/d=0, short=r=0/w=0/d=0, drop=r=0/w=0/d=0
latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs):
READ: io=9915.2MB, aggrb=991.23MB/s, minb=991.23MB/s, maxb=991.23MB/s, mint=10003msec, maxt=10003msec
Disk stats (read/write):
vdb: ios=98460/0, merge=0/0, ticks=48840/0, in_queue=49144, util=17.28%
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