Strange problem with... ZFS? Disk? Controller?

[Alex Povolotsky]

Hello,

I'm running FreeBSD 9.0/amd64, pure ZFS setup, one Seagate disk 
ST2000NM0011 SN02 on LSI Logic (mpt) controller.

Yes, I know that running one disk on RAID controller is a bit weird, I 
have to find yet if it is possible to connect disk to internal SATA 
controller.

About two days ago, system became SLOW. Disk usage is constantly 100%, 
and sometimes I'm getting swap_pager: indefinite wait buffer error. I 
had to reset computer twice in two days.

mptutil does not show any errors, and smartctl shows

SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE UPDATED  
WHEN_FAILED RAW_VALUE
   1 Raw_Read_Error_Rate     0x000f   067   063   044    Pre-fail 
Always       -       6218970
   3 Spin_Up_Time            0x0003   093   092   000    Pre-fail 
Always       -       0
   4 Start_Stop_Count        0x0032   100   100   020    Old_age 
Always       -       14
   5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail 
Always       -       21
   7 Seek_Error_Rate         0x000f   091   060   030    Pre-fail 
Always       -       1433294073
   9 Power_On_Hours          0x0032   090   090   000    Old_age 
Always       -       8825
  10 Spin_Retry_Count        0x0013   100   100   097    Pre-fail 
Always       -       0
  12 Power_Cycle_Count       0x0032   100   100   020    Old_age 
Always       -       16
184 End-to-End_Error        0x0032   100   100   099    Old_age 
Always       -       0
187 Reported_Uncorrect      0x0032   100   100   000    Old_age 
Always       -       0
188 Command_Timeout         0x0032   100   099   000    Old_age 
Always       -       12885098499
189 High_Fly_Writes         0x003a   100   100   000    Old_age 
Always       -       0
190 Airflow_Temperature_Cel 0x0022   068   047   045    Old_age 
Always       -       32 (Min/Max 31/32)
191 G-Sense_Error_Rate      0x0032   100   100   000    Old_age 
Always       -       859
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age 
Always       -       15
193 Load_Cycle_Count        0x0032   100   100   000    Old_age 
Always       -       26
194 Temperature_Celsius     0x0022   032   053   000    Old_age 
Always       -       32 (0 21 0 0 0)
195 Hardware_ECC_Recovered  0x001a   103   099   000    Old_age 
Always       -       6218970
197 Current_Pending_Sector  0x0012   100   100   000    Old_age 
Always       -       0
198 Offline_Uncorrectable   0x0010   100   100   000    Old_age 
Offline      -       0
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age 
Always       -       0

SMART Error Log Version: 1
No Errors Logged

I have removed most of snapshots, it does not help.

I have stopped all active processes, disk load did not decrease, same 100%.

What can I check and/or replace to get the problem fixed? Any ideas?

Alex