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Date:      Sun, 29 Sep 1996 05:29:13 +0930 (CST)
From:      Peter Childs <pjchilds@imforei.apana.org.au>
To:        bsdscsi@shadows.aeon.net (mika ruohotie), freebsd-scsi@freebsd.org
Subject:   Re: striping/mirroring?
Message-ID:  <199609281959.FAA23341@al.imforei.apana.org.au>

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: > Thus if you were to mirror a 4 drive combination to a single drive, that
: > drive would have to be 4 times as large. It would also need to be fast.

: it should be huge, yes. fast, no, if i dont want to mirror all i am
: striping... or if i do the way i was planning... using 2 gig drives,
: and only _use_ the space of one disk i'm mirroring to...

 I'm really quite interested in how you propose to have a mirrored
 system where drives can run at different steeds.   Mirror works like
 this

 DATA ----> (going to disk) -------+--(and another copy)----+
                                   |                        |
                                disk 1                   disk 2

 So if i send some data to the (mirrored) disk, and disk1
 is significantly faster than disk2, then disk1 will finish the write
 first.... so then do i just let it write more?   Can you see a 
 problem with this?   What happens when disk1 is miles ahead.. who
 is supposed to keep track of all this data thats queued up for
 disk2?  The OS?  And if the disk 1 suddenly fails then you're
 screwed, and you fault tolerant system wan't very.

: original question was, can i do it with freebsd?

: seems to me answer is no.

 The reason FreeBSD can't do it is because the only people 
 capable of writting it know that its not really the best idea.

 Peter

--
 Peter Childs  ---  http://www.imforei.apana.org.au/~pjchilds
  Finger pjchilds@al.imforei.apana.org.au for public PGP key
         Drag me, drop me, treat me like an object!



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