zfs read error without disk error.

[Bernd Walter]

I've upgraded my system to recent 8 and switched disks to CAM.
Since I've been seeing CRC errors from time to time I've decided to
start a scrub.
My disks are connected to Inteln AHCI onboard and SiI 3132 with CAM.
I have an SSD cache device attached to SiI3114 (cache6) with ata driver.
And i have 4 USB flash sticks for additional cache.
The system is booting with UFS from a 4G CF media attached to a SiI 680.

Now I see the following:
[156]cicely14# zpool status -v
  pool: data
 state: ONLINE
status: One or more devices has experienced an unrecoverable error.  An
        attempt was made to correct the error.  Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
        using 'zpool clear' or replace the device with 'zpool replace'.
   see: http://www.sun.com/msg/ZFS-8000-9P
 scrub: scrub in progress for 24h46m, 67.17% done, 12h6m to go
config:

        NAME             STATE     READ WRITE CKSUM
        data             ONLINE       0     0     0
          raidz1         ONLINE       0     0     0
            ada6         ONLINE       0     0     0
            ada3         ONLINE       0     0     0
            ada5         ONLINE       1     0     0  42.5K repaired
            ada4         ONLINE       0     0     0
          raidz1         ONLINE       0     0     0
            ada0         ONLINE       0     0     5  13K repaired
            ada1         ONLINE       0     0     0
            ada7         ONLINE       0     0     1  14K repaired
            ada2         ONLINE       0     0     0
        cache
          label/cache6   ONLINE       0     0     0
          label/cache7   ONLINE       4     0     0
          label/cache8   ONLINE       2     3     0
          label/cache9   ONLINE       2     2     0
          label/cache10  ONLINE       1     3     0

errors: No known data errors

Kernel just has:
(da2:umass-sim2:2:0:0): AutoSense failed
(da0:umass-sim0:0:0:0): AutoSense failed
(da2:umass-sim2:2:0:0): AutoSense failed
(da1:umass-sim1:1:0:0): AutoSense failed
(da3:umass-sim3:3:0:0): AutoSense failed

Probably the USB AutoSense failed have something to do with the cache
device read/write errors, but they are not listed as read read/write
errors.
The checksum errors are of unknown reason, but of course not mentioned
by the kernel, but ada5 also has a read error for which the kernel has
no message either.

[158]cicely14# camcontrol devlist -v
scbus0 on siisch0 bus 0:
<ST3500630AS 3.AAC>                at scbus0 target 0 lun 0 (pass0,ada0)
<>                                 at scbus0 target -1 lun -1 ()
scbus1 on siisch1 bus 0:
<ST3500630AS 3.AAC>                at scbus1 target 0 lun 0 (pass1,ada1)
<>                                 at scbus1 target -1 lun -1 ()
scbus2 on siisch2 bus 0:
<ST3500630AS 3.AAC>                at scbus2 target 0 lun 0 (pass2,ada2)
<>                                 at scbus2 target -1 lun -1 ()
scbus3 on siisch3 bus 0:
<ST3500630AS 3.AAC>                at scbus3 target 0 lun 0 (pass3,ada3)
<>                                 at scbus3 target -1 lun -1 ()
scbus4 on ahcich0 bus 0:
<ST3500630AS 3.AAK>                at scbus4 target 0 lun 0 (pass4,ada4)
<>                                 at scbus4 target -1 lun -1 ()
scbus5 on ahcich1 bus 0:
<ST3500630AS 3.AAK>                at scbus5 target 0 lun 0 (pass5,ada5)
<>                                 at scbus5 target -1 lun -1 ()
scbus6 on ahcich2 bus 0:
<>                                 at scbus6 target -1 lun -1 ()
scbus7 on ahcich3 bus 0:
<>                                 at scbus7 target -1 lun -1 ()
scbus8 on ahcich4 bus 0:
<ST3500630AS 3.AAK>                at scbus8 target 0 lun 0 (pass6,ada6)
<>                                 at scbus8 target -1 lun -1 ()
scbus9 on ahcich5 bus 0:
<ST3500630AS 3.AAC>                at scbus9 target 0 lun 0 (pass7,ada7)
<>                                 at scbus9 target -1 lun -1 ()
scbus10 on umass-sim0 bus 0:
<USB2.0 FlashDisk 0.00>            at scbus10 target 0 lun 0 (da0,pass8)
scbus11 on umass-sim1 bus 1:
<USB2.0 FlashDisk 0.00>            at scbus11 target 0 lun 0 (da1,pass9)
scbus12 on umass-sim2 bus 2:
<USB2.0 FlashDisk 0.00>            at scbus12 target 0 lun 0 (da2,pass10)
scbus13 on umass-sim3 bus 3:
<USB2.0 FlashDisk 0.00>            at scbus13 target 0 lun 0 (da3,pass11)
scbus-1 on xpt0 bus 0:
<>                                 at scbus-1 target -1 lun -1 (xpt0)

[159]cicely14# atacontrol list
ATA channel 2:
    Master:      no device present
    Slave:       no device present
ATA channel 3:
    Master:      no device present
    Slave:       no device present
ATA channel 4:
    Master:      no device present
    Slave:       no device present
ATA channel 5:
    Master: ad10 <TS32GSSD25S-M/V090331> SATA revision 2.x
    Slave:       no device present
ATA channel 6:
    Master:      no device present
    Slave:       no device present
ATA channel 7:
    Master: ad14 <TRANSCEND/20080128> ATA/ATAPI revision 4
    Slave:       no device present
ATA channel 8:
    Master: ad16 <TRANSCEND/20070831> ATA/ATAPI revision 0
    Slave:       no device present

-- 
B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.