Re: [Bug-ddrescue] 10KB/sec data recovery rates - possible cause?

[Scott D]

On 6/21/2013 3:27 AM, Paul L Daniels wrote:
> On Tue, 18 Jun 2013 20:12:32 +1000
> Paul L Daniels <address@hidden> wrote:
>
>
> >         I have a client 1TB WD 2.5" drive from a portable enclosure
> >         which failed on their system.  On start up there's no clanking
> >         or banging ( good sign! ) but it's *incredibly* slow to read,
> >         we're talking a peak of ~15KB/sec and an average of 10KB/sec.
> FURTHERING to this... I've noticed that every time I restart ddrescue
> I'll get the first 2MB or so in at a much higher rate for a short burst
> until it drops back to the ~15KB/sec.
>
> Does ddrescue initialise anything special at the start that could
> possibly explain this behaviour?
>
> It's not a time-shift/hiccup transient, because if I put a 1 second
> delay between each update it'll transfer it in 32KB blocks/sec until
> again it runs in to that ~2MB limit.
>
> Paul.
Are you using the -d option for direct disk access? I have noticed slow 
downs like that, but using the direct disk access option seemed to take 
care of that and resulted in much faster reads.