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Date:      Mon, 27 Dec 1999 13:35:07 +1030
From:      Greg Lehey <grog@lemis.com>
To:        Gary Palmer <gjp@in-addr.com>
Cc:        current@freebsd.org
Subject:   Re: ``how to'' for Vinum and mirroring after the volume was created?
Message-ID:  <19991227133507.X1316@freebie.lemis.com>
In-Reply-To: <41935.946261455@noop.colo.erols.net>
References:  <19991227123124.U1316@freebie.lemis.com> <41935.946261455@noop.colo.erols.net>

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On Sunday, 26 December 1999 at 21:24:15 -0500, Gary Palmer wrote:
> Greg Lehey wrote in message ID
> <19991227123124.U1316@freebie.lemis.com>:
>> It occurs to me that it is, in fact, correct to read from a volume
>> being revived.  The data is consistent up to the point where the
>> revive has progressed, so the system can read from this area.
>
> Why would it be reading from the reviving plex?  The volume wasn't
> mounted when I was watching the stats, so the only i/o should have
> been the revive.  (Yes, I'm paranoid :) )

Again, news for me.  You can stop a revive and restart it at a later
time; the state information includes the revive pointer.  But the only
real answer to this one would be to see the statistics.

>> Hmm.  This looks too VERITAS-like for my liking.  In addition, this
>> isn't a flag.  Internally it's represented as a plex index, with -1
>> meaning "round robin".
>
> Aaah.  That makes sense.
>
>> I've tried to keep away from this sort of stuff.
>
> Unfortunately a beast as complicated as a LVM has to have the ability
> to change the way it works on the fly.

You misunderstand.  I've tried to stay away from the complexity of the
VERITAS syntax.  Sure, I agree that being able to reconfigure on the
fly is important.

>> The second example is supposed to set round robin.  I don't like that
>> syntax either.  Maybe the second example should be just
>>
>>   vinum prefer volfoo.
>
> vinum prefer volfoo none
>
> That runs into problems with people calling plexes `none', but in that
> case they get what they deserve ;)

Right, that's the down side.  I suppose we could include the
alternative of a plex index in the syntax.

> vinum prefer volfoo ""
>
> There is some precedent for the null string being used for stuff like
> this.  I can't think of them offhand, but some unix programs take that
> sort of flag.

Right, but it's confusing for people new to UNIX.

Greg
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