immense delayed write to file system (ZFS and UFS2), performance issues

[Matthew Dillon]

    Here's what I got from one of my 2TB WD green drives.  This one
    is Firmware 01.00A01.  Load_Cycle_Count is 26... seems under
    control.

    It gets hit with a lot of activity separated by a lot of time
    (several minutes to several hours), depending on what is going on.
    The box is used for filesystem testing.  Regardless it seems to
    stay spun-up all the time, or nearly all the time.

    Neither the BIOS nor the kernel driver is messing with the SUD
    control on the Silicon Image board it is connected to (other
    then just turning it on and leaving it that way).  If the
    drive has an intelligent parking function it doesn't seem to
    be using it much.  I haven't specifically disabled any such
    function.

Device Model:     WDC WD20EADS-00R6B0
Serial Number:    WD-WCAVY0259672
Firmware Version: 01.00A01
User Capacity:    2,000,398,934,016 bytes
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   8
ATA Standard is:  Exact ATA specification draft version not indicated
Local Time is:    Tue Jan 26 19:25:48 2010 PST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

...
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x002f   200   200   051    Pre-fail  Always       -       0
  3 Spin_Up_Time            0x0027   212   150   021    Pre-fail  Always       -       6375
  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       39
  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x002e   200   200   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   095   095   000    Old_age   Always       -       4252
 10 Spin_Retry_Count        0x0032   100   253   000    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0032   100   253   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       37
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       13
193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       26
194 Temperature_Celsius     0x0022   121   111   000    Old_age   Always       -       31
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0030   200   200   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       0

    I have a few of these babies strewn around.  The others show about
    the same stats, e.g. this one is used in a production box.  Same
    drive type, same firmware:

ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  9 Power_On_Hours          0x0032   095   095   000    Old_age   Always       -       4164
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       43
193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       26
...

    So on the face of it things seem ok with these drives.  Presumably WD
    is working adjustments into the firmware as time goes on.  Hopefully
    they aren't just masking the count in the SMART page to appease
    techies :-)

    These particular WDs (2TB Caviar Green's) are slow drives.  5600 rpm,
    100MB/sec.  But they are also very quiet in operation and seem to
    be quite power efficient.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>