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Date:      Thu, 20 Jul 2000 18:33:42 +0930
From:      Greg Lehey <grog@lemis.com>
To:        Geoff Buckingham <geoffb@chuggalug.clues.com>
Cc:        hackers@FreeBSD.ORG, scsi@FreeBSD.ORG
Subject:   Re: Multiple ro mounts of vinum volume
Message-ID:  <20000720183341.I30599@wantadilla.lemis.com>
In-Reply-To: <20000720095513.A50799@chuggalug.clues.com>
References:  <20000720095513.A50799@chuggalug.clues.com>

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On Thursday, 20 July 2000 at  9:55:13 +0100, Geoff Buckingham wrote:
>
> Does anybody with a knowledge of the vinum code have an opinion on
> the amount of work involved in getting vinum to the point that
> several JBODs in a FC switched fabric could be managed, as a vinum
> volume, by one machine, and mounted ro by that machine and several
> others on the switch fabric.

I'd say "no work at all" as far as Vinum is concerned.  The real issue
is getting the drivers to present the individual drives to the
system.  That's a device driver issue, and I don't know enough about
the current state of FC drivers to make a sensible comment.  But I'd
certainly be interested to hear more.

> (writing to that volume is obviously a fs issue)

That depends if you want to put a file system on it.

A thing that might bite you here is that ufs is currently limited to 1
TB per volume.  Vinum doesn't have that restriction: if you want to
create a 20 TB volume, and you know how to use the space, Vinum should
work.  The problem with ufs is that the block numbers in the inodes
are 32 bit signed values.  With 512 byte sectors, the only we can do
it, that means a total address space of 2**9 * 2*31, or 1 TB.  At some
time I suspect we're going to need to fix that.

Greg
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