rsize/wsize and Samba performance

[Steve French]

Any idea why Samba performance is worse with 8MB i/os than 1MB i/os for
sequential
read/write multiple process i/os?   Performance was good ... but it
surprised me that 1MB was better than 8MB

The fio job file I was using was the normal fio-seq-RW
# cat ~/fio/fio-seq-RW.job
[global]
name=fio-seq-RW
filename=fio-seq-RW
rw=rw
rwmixread=60
rwmixwrite=40
bs=256K
direct=0
numjobs=4
time_based=1
runtime=100

[file1]
size=10G
ioengine=libaio
iodepth=16


SMB3.02 mounts to Samba

rsize/wsize default (ie 1MB on Linux client)
   READ: bw=3098MiB/s (3249MB/s), 773MiB/s-776MiB/s (810MB/s-814MB/s),
io=303GiB (325GB), run=100001-100002msec
  WRITE: bw=2071MiB/s (2172MB/s), 518MiB/s-518MiB/s (543MB/s-543MB/s),
io=202GiB (217GB), run=100001-100002msec

---------------------------------------------

rsize/wsize=8MB mount on Linux client
   READ: bw=2779MiB/s (2913MB/s), 692MiB/s-696MiB/s (726MB/s-730MB/s),
io=271GiB (291GB), run=100001-100001msec
  WRITE: bw=1858MiB/s (1948MB/s), 464MiB/s-465MiB/s (487MB/s-487MB/s),
io=181GiB (195GB), run=100001-100001msec

NFSv3 and NFSv4.1 as expected (to kernel NFS server) were much slower than
SMB3 for both read and write (presumably Samba is handling more I/Os and
doing better job async - i/o sizes are now the same 1MB by default)
-- 
Thanks,

Steve