odd behavior with geom - gmirror - read/write simultaneously

[Thiago Damas]

  Hi,
  I'm having a odd behavior while using geom_mirror.
  I have the following situation:
- RAID1 with 2 SATA disks
# gmirror status
        Name    Status  Components
mirror/home0  COMPLETE  ad2
                        ad3

- home0 as /home
# df -h
Filesystem              Size    Used   Avail Capacity  Mounted on
/dev/ad0s1a             1.9G     74M    1.7G     4%    /
devfs                   1.0K    1.0K      0B   100%    /dev
/dev/ad0s1d             989M     16K    910M     0%    /tmp
/dev/ad0s1e             7.7G    1.9G    5.2G    27%    /usr
/dev/ad0s1f              58G    139M     53G     0%    /var
/dev/mirror/home0s1c    226G    7.4G    200G     4%    /home

  I was testing the read/write speed on /home, with:
# dd if=/dev/ad0 of=/home/test.data bs=4m
  While running this, gstat shows me what I wanted:
# gstat
 L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
    0    230    230  29383    1.9      0      0    0.0   42.8| ad0
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1
    9    192      0      0    0.0    192  24529   21.0   65.3| ad2
    7    196      0      0    0.0    196  25040   16.6   65.4| ad3
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1a
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1b
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1c
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1d
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1e
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1f
    0      0      0      0    0.0      0      0    0.0    0.0| ad2s1
    9    192      0      0    0.0    192  24529   21.2   65.4| mirror/home0
    0      0      0      0    0.0      0      0    0.0    0.0| ad3s1
    9    192      0      0    0.0    192  24529   21.2   65.4| mirror/home0s1
    9    192      0      0    0.0    192  24529   22.0   66.6| mirror/home0s1c

  After that, I test the read speed:
# dd if=/home/test.data bs=4m of=/dev/null
# gstat
dT: 0.501  flag_I 500000us  sizeof 240  i -1
 L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
    0      0      0      0    0.0      0      0    0.0    0.0| ad0
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1
    1    120    120  15329    3.7      0      0    0.0   44.9| ad2
    0    122    122  15584    3.5      0      0    0.0   43.1| ad3
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1a
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1b
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1c
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1d
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1e
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1f
    0      0      0      0    0.0      0      0    0.0    0.0| ad2s1
    1    242    242  30913    3.7      0      0    0.0   88.4| mirror/home0
    0      0      0      0    0.0      0      0    0.0    0.0| ad3s1
    1    242    242  30913    3.7      0      0    0.0   88.7| mirror/home0s1
    1    242    242  30913    3.7      0      0    0.0   90.0| mirror/home0s1c

 And it shows again what was supposed to.

  Now, I test read/write simultaneously:
In on shell (1):
# dd if=/dev/ad0 of=/home/test.data bs=4m
After some time, in another shell(2)
# dd if=/home/test.data bs=4m of=/dev/null
  And gstat shows me the following:
# gstat
dT: 0.501  flag_I 500000us  sizeof 240  i -1
 L(q)  ops/s    r/s   kBps   ms/r    w/s   kBps   ms/w   %busy Name
    0      0      0      0    0.0      0      0    0.0    0.0| ad0
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1
    0    158    158  20183    3.0      0      0    0.0   47.6| ad2
    1    158    158  20183    2.5      0      0    0.0   39.1| ad3
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1a
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1b
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1c
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1d
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1e
    0      0      0      0    0.0      0      0    0.0    0.0| ad0s1f
    0      0      0      0    0.0      0      0    0.0    0.0| ad2s1
    1    315    315  40367    2.8      0      0    0.0   87.4| mirror/home0
    0      0      0      0    0.0      0      0    0.0    0.0| ad3s1
    1    315    315  40367    2.8      0      0    0.0   87.8| mirror/home0s1
    1    315    315  40367    2.8      0      0    0.0   89.4| mirror/home0s1c


  I'm having NO writes in home0; even hitting ^C in shell(1) hangs,
until I cancel the dd command in shell(2).
  I think its happening some problem with geom code . Can someone
verify this? I using 6.1 PRERELEASE, with GENERIC kernel.

---
Thiago