[Dirvish] checksum=0 may be causing inaccurate backups!!!

Keith Lofstrom keithl at kl-ic.com
Thu Jun 21 13:32:03 UTC 2007


On Thu, Jun 21, 2007 at 03:17:21AM -0700, Barton C Massey wrote:
> I can think of no reason why checksumming should add 6x to
> the backup time.  Am I missing something?
> 
> 	Bart

Because dirvish/rsync normally reads only metadata off the disk,
whereas checksumming reads every byte.  The 6X worst case is 
when both the source and backup drives are on the same machine.
It's all read time, at 1.2GB/minute in some cases, and that can
take a LONG time.

BTW, I woke to nightmares about this, see the major warning in
the next message before doing "checksum=1=".

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs


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