ad0 READ_DMA TIMEOUT errors on install of 7.0-RELEASE

[Alex Zbyslaw]

Stephen Hurd wrote:

> Jeremy Chadwick wrote:
>
>>> SMART Attributes Data Structure revision number: 16
>>> Vendor Specific SMART Attributes with Thresholds:
>>> ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      
>>> UPDATED  WHEN_FAILED RAW_VALUE
>>>   5 Reallocated_Sector_Ct   0x0033   253   253   063    Pre-fail  
>>> Always       -       4 
>>
>> This shows you've had 4 reallocated sectors, meaning your disk does in
>> fact have bad blocks.  In 90% of the cases out there, bad blocks
>> continue to "grow" over time, due to whatever reason (I remember reading
>> an article explaining it, but I can't for the life of me find the URL).  
>
>
> This is unusual now?  I've always "known" that a small number of bad 
> blocks is normal.  Time to readjust my knowledge again?

I have bought disks where the value of Reallocated_Sector_Ct was not 0, 
at least by the time I looked at it with smartctl.  Nothing bad has 
happened to those disks in several years (hope that's not tempting fate).

I have always assumed that what matters is when this value *changes*.  
If it's not changing, who cares?  smartd will monitor disks and email 
you when certain attributes change (e.g. Pre-fail attributes like 
Reallocated_Sector_Ct).  If it changed, it would mean that an attempt to 
write data  had failed and that reallocation had happened.

e.g. from smartd.conf

/dev/ad4 -o on -S on -a -m root -M daily

If your Current_Pending_Sector were non-zero you'd be in trouble, I believe.

0.02, pinch of salt, not an expert, slippery when hot, long time since I 
read the specs, etc etc.

--Alex