[H-GEN] Clock Time Loss When Copying Files

Martin Pool mbp at linuxcare.com.au
Tue Jun 6 21:38:17 EDT 2000


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On Wed, 7 Jun 2000, Frank Brand wrote:

> A friend of mine is copying the full contents of his drive to a drive in
> another machine. He does this periodically as a form of backup. He has also
> done this with another box as well.
> 
> The copy is over a 10 Mb BNC link.
> 
> It seems that wheh he does this the clock on the box being copied loses time.

I wonder if the machine is masking out timer interrupts while doing IO,
and so losing time.  (Is it a slow machine or hard drive?)  In that case
it would be interesting to see what the hardware real-time-clock says
compared to the system clock.  If it is accurate, then you can use it to
reset the system clock at regular intervals, or you could run NTP.

So, looking at /proc/interrupts over time might tell you
something.  (i.e. Are there as many timer interrupts as there should
be?  Does it vary with load?)

I think I've heard of it happening using IDE CDROM burners. 

Have you thought of using rsync to reduce the amount of data
copied? :-) <http://samba.org/rsync/>

Hm.  I'd be interested to see how it turns out.

-- 
Martin Pool, Linuxcare, Inc.
+61 2 6262 8990
mbp at linuxcare.com, http://www.linuxcare.com/
Linuxcare. Support for the revolution.


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