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Date: Fri, 4 Nov 2005 09:30:27 +1100
From: Peter Clutton <peterclutton@gmail.com>
To: Steve Bertrand <iaccounts@ibctech.ca>
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Cc: freebsd-questions@freebsd.org
Subject: Re: gmirror on 1 or 2 IDE cables
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On 11/4/05, Steve Bertrand <iaccounts@ibctech.ca> wrote:
>
> > Using gmirror to mirror two identical drives, how much of a
> > performance hit is it to have
> >
> > 1.  Both drives on one IDE cable?
> > Compared to:
> > 2.  One drive primary on one cable and one secondary on the
> > other cable?
> > Compared to:
> > 3.  Both drives primary but on separate IDE cables?
>
> My understanding that only a single drive on each IDE channel can be
> accessed at any one time.
>
> Thus, if you put one drive on one channel, and the other drive on the
> second channel, they can be accessed simultaneously. The location on the
> cable(s) does not matter,

That is correct about the two channels, one should be on each. However
it does make a difference as to primary or secondary, if you have
other drives attached (such as cdrom). Try putting the cdrom as
primary, then secondary, and have a watch to discover the difference.
This might not be noticed with a normal secondary hard drive, as you
may not write to it much. However in a mirror the second is always
written to, and you will notice the difference if you are also using
the cdrom