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Re: Disk performance deteriated to unbearable levels

On 09/11/11 12:50, Alberto Luaces wrote:

Miles Fidelman writes:


Stan Hoeppner wrote:

On 11/9/2011 1:34 AM, Bob Proulx wrote:

Miles Fidelman wrote:

try smartctl -A /dev/sda

that will give you a much longer list of statistics collected by
the drive

the one I always look at first is the absolute value of "raw read
errors" - if that's higher than 0, the drive is starting to fail,
and its internal code is spending more and more time trying to read
and re-read data off the media

Excellent information!

Not really.  The numbers are not absolutes.  And they differ among
manufacturers.  S.M.A.R.T. is a data format standard for "drive
health", but it does not dictate "value" standards for the field
contents.

For the end user, attempting to interpret some S.M.A.R.T. data for
some makes of drives is hit or miss.  I would say as a general rule
that one should contact the drive manufacturer if s/he sees
S.M.A.R.T. error counts rise.  The drive may or may not be failing.


Specifically for "raw read error" - in the format

ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED
RAW_VALUE
   1 Raw_Read_Error_Rate 0x000b 088 088 062 Pre-fail Always - 3342368

I've found, across many different dries, that the "VALUE" field (which
is a relative field calculated over time) is generally useless, while
the RAW_VALUE field is almost always indicative of pending failure if
it's value is anything other than 0.


All my drives have a RAW_VALUE for that parameter not equal to 0:

machine1$ sudo smartctl -A /dev/sdb | grep "Read\|Power_On"
   1 Raw_Read_Error_Rate     0x000f   108   099   006    Pre-fail  Always       -       18696503
   9 Power_On_Hours          0x0032   087   087   000    Old_age   Always       -       11987

machine1$ sudo smartctl -A /dev/sda | grep "Read\|Power_On"
   1 Raw_Read_Error_Rate     0x000f   111   086   006    Pre-fail  Always       -       35575453
   9 Power_On_Hours          0x0032   069   069   000    Old_age   Always       -       27906

Even with new drives:

machine2$ sudo smartctl -A /dev/sdb | grep -e "Read\|Power_On"
   1 Raw_Read_Error_Rate     0x000f   117   100   006    Pre-fail  Always       -       131149163
   9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       475
machine2$ sudo smartctl -A /dev/sdc | grep -e "Read\|Power_On"
   1 Raw_Read_Error_Rate     0x000f   111   100   006    Pre-fail  Always       -       31090694
   9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       285

Those are all Seagate drives. Maybe their raw value means something
different.
Maybe. Power_On_Hours will be almost always be greater than zero, but Raw_Read_Error_Rate is showing as zero on all my drives. 

--
Dom
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