Re: [Bug-ddrescue] SMART, reallocation, and retries

[Christian Franke]

Franc Zabkar wrote:
> May I suggest that ddrescue disable SMART by default, if it does not 
> already do so. 

The SMART DISABLE command does not necessarily disable internal 
monitoring and sector reallocation. It only disables the SMART related 
ATA commands.


> Also I believe that there may be ATA commands that allow retries to be 
> disabled at the drive level, at least in earlier versions of the 
> standard.
>
>  Read DMA Without Retries
>  Read Sectors Without Retry
>  Set Features Disable Retry

All the above commands were declared obsolete in ATA-5 (~2000). Do you 
have any evidence that these commands are still supported by a 
reasonable number of recent (ATA-8 ACS and later) drive models?

Ddrescue currently builds and works out of the box on most POSIX 
platforms (including Windows thanks to Cygwin). It does not require 
platform specific hacks.

Adding things like disable SMART or specific ATA READ commands would 
introduce the full "there is no standard ATA/SCSI pass-through 
functionality (and the existing non-standard functions do not work with 
all controllers)" problem to ddrescue. This makes e.g. smartmontools 
rather complex and prevents that Linux hdparm could be easily ported.


> Perhaps Error Recovery Control (ERC) and the ATA Streaming feature set 
> might be useful in the above regard.

Try "smartctl -l scterc,R,W /dev/ice" before using ddrescue. Many recent 
disks support ERC/TLER, even normal "desktop" (non-RAID) series.

Regards,
Christian