Date: Fri, 4 Nov 2005 09:30:27 +1100 From: Peter Clutton <peterclutton@gmail.com> To: Steve Bertrand <iaccounts@ibctech.ca> Cc: freebsd-questions@freebsd.org Subject: Re: gmirror on 1 or 2 IDE cables Message-ID: <57416b300511031430p72165a8av386da275c1db748e@mail.gmail.com> In-Reply-To: <20051103152751.C48FC43D49@mx1.FreeBSD.org> References: <00b801c5e087$b7aa3840$c901a8c0@workdog> <20051103152751.C48FC43D49@mx1.FreeBSD.org>
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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
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