From mboxrd@z Thu Jan  1 00:00:00 1970
From: smiley@icebubble.org
To: 9fans@9fans.net
Date: Mon, 26 Nov 2012 06:04:03 +0000
Message-ID: <86haochpd8.fsf@cmarib.ramside>
MIME-Version: 1.0
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Subject: [9fans] growing/shrinking venti arena files -OR- arena file format
Topicbox-Message-UUID: e485f48e-ead7-11e9-9d60-3106f5b1d025

Hello,

I'm wondering if anyone can shed some light on growing and/or shrinking
arena files (i.e., disk partitions).  With the growing popularity of
logical volume management, vitrualization, etc., resizing partitions is
becoming more and more common, and many file systems already have
"resize" tools or options to grow/shrink file system structures
according to changes in the size of the underlying device.  I'm
wondering what capacities (if any) venti has for dealing with inceases
or decresases in the size of its arena files.

Yes, I know that the canonical way to add more storage to a venti server
is to format and add an ADDITIONAL arena file with venti/fmtindex -a.
But I'd like to know, specifically, if it's possible to grow/shrink an
arena file without breaking anything.  If an arena file is extended,
will venti automatically make use of the extra space?  Would the
additional arenas need to be formatted?  And, if so, how?  If empty
arenas at the end of an arena file are truncated (on an arena boundary,
ideally), would venti continue to function properly, fill up the
remaining space, and then continue on to the next arena file?  Or, would
venti crash and burn in a pile of flaming bits and bytes?

Another way of stating this question might be to ask for information
about the arena file format.  Knowing the file format, I could deduce
whether any inconsistency would be introduced by a change in file size.
Yes, I read the venti paper, including its descripion of arena files and
their contents.  However, it is rather vague on such points, more like
an academic lecture or advertisement than a technical specification.  Is
there a TECHNICAL SPECIFICATION for the arena file format?  Getting my
eyeballs on one would probably allow me to figure this all out, for
myself.  For that matter, any formal specifications for 9P2000 and the
venti protocol would be very helpful, too (for other purposes).

Any pointers (dereferenced or not :) would be greatly appeciated!

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