ZFS reports problem on iscsi target

[Rolf Grossmann]

Hi,

I'm having some trouble with iscsi on FreeBSD 8. My current setup is a
stock FreeBSD 8.1-PRERELEASE (as of 2 days ago), GENERIC kernel with
some modules loaded, running on a Dell PowerEdge R905 with 64GB RAM, 4
quad code CPUs. Attached is an EqualLogic PS6500 storage array with some
configured volumes, one of which is for testing. It is configured in
/etc/iscsi.conf like this:

test2 {

TargetName=iqn.2001-05.com.equallogic:0-8a0906-7a4bb9f06-038000000304c0d1-test2
  TargetAddress=10.26.17.10:3260,1
  tags = 256
}

Now I'm running the following sequence of commands (shown with output):

# iscontrol -n test2
iscontrol[56255]: running
iscontrol[56255]: (pass2:iscsi0:0:0:0):  tagged openings now 256
iscontrol[56255]: cam_open_btl: no passthrough device found at 2:0:1
iscontrol[56255]: cam_open_btl: no passthrough device found at 2:0:2
iscontrol[56255]: cam_open_btl: no passthrough device found at 2:0:3
iscontrol: supervise starting main loop
# zpool create test2 da2
# zpool scrub test2
# zpool status test2
  pool: test2
 state: ONLINE
 scrub: scrub completed after 0h0m with 0 errors on Fri Jun 11 16:56:33 2010
config:

        NAME        STATE     READ WRITE CKSUM
        test2       ONLINE       0     0     0
          da2       ONLINE       0     0     0

errors: No known data errors
# cp -Rp /export/system /test2/
# zpool scrub test2
# zpool status test2
  pool: test2
 state: ONLINE
status: One or more devices has experienced an error resulting in data
        corruption.  Applications may be affected.
action: Restore the file in question if possible.  Otherwise restore the
        entire pool from backup.
   see: http://www.sun.com/msg/ZFS-8000-8A
 scrub: scrub completed after 0h0m with 19 errors on Fri Jun 11 17:00:38
2010
config:

        NAME        STATE     READ WRITE CKSUM
        test2       ONLINE       0     0    19
          da2       ONLINE       0     0    38

errors: 19 data errors, use '-v' for a list
#

/export/system is a FreeBSD distribution (make install
DESTDIR=/export/system). Note how zfs thinks there are 19 files broken
after the copy. If I repeat the process, the files vary, but there are
always some reported as broken. In this case, they don't seem to be (as
checked with md5 and rsync --checksum), but I've had files only giving
me an i/o error. Also, if I repeat the same steps on a local disk, zfs
is reporting no errors.

What I would like to know is:
- Is there anything I'm doing wrong? Is there a known problem?
- Are there any tools to debug or more reliably reproduce (and narrow
down) the problem? I've tried fsx (from /usr/src/tools/regression), but
I couldn't find any usage suggestions (other than the usage when run
without options) and it doesn't complain when run.
- On a different system I've tried using a newer iscsi version from
http://www.cs.huji.ac.il/~danny/ftp/freebsd/ but it didn't make any
difference. Is that still preferable?

Some help would be appreciated.

Thanks, Rolf.