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Date:      Thu, 8 Apr 1999 11:55:23 +0200 (CEST)
From:      Remy Nonnenmacher <remy@synx.com>
To:        grog@lemis.com
Cc:        hackers@FreeBSD.ORG
Subject:   Re: Volume managers (was: Separate boot partition?)
Message-ID:  <199904080955.LAA08304@rt2.synx.com>
In-Reply-To: <19990408182917.G2142@lemis.com>

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On  8 Apr, Greg Lehey wrote:
> On Thursday,  8 April 1999 at 10:44:15 +0200, Remy Nonnenmacher wrote:
>> On  8 Apr, Greg Lehey wrote:
>>> On Thursday,  8 April 1999 at  8:52:24 +0100, Dom Mitchell wrote:
>>>> On 8 April 1999, Greg Lehey proclaimed:
>>>>> I can't see why not, since it's possible now.  What we still need to
>>>>> do is find a way to extend a file system, but that's a ufs issue
>>>>> (which has a solution), not a volume manager issue.
>>>>
>>>> What about shrinking an fs?  Is that feasible?  Possible?
>>>
>>> According to Kirk McKusick, no.
>>>
>> too bad !!
>>
>> Really, merging the best of all worlds (AIX PV migration, fs 'live'
>> extendability) *AND* fs shrinking would be a really impressive
>> performance.
>>
>> Think about it : A set of SCA, hot-pluggable disks. Every fs movable,
>> resizable (up/down), every disk content movable from/to every other
>> one.... the perfect power-on once, run till-end-of-universe server.
> 
> Well, with the exception of the file system shrinking, we have all
> that.  I honestly don't think we'll find a need to shrink file systems
> too often.
>

Sure, but 'not too often' is not 'never' and when case raises, for
exemple with these messages : (assuming you can't hot-add disks...)

- "too bad: you are 100MB too short on this fs. 200MB are wasted here
and here. watch and cry!!"
- "Ha Ha !! 100MB needed for install, 50 MB available. Anyway, have a
look around there: 10 fs with 50MB wasted on each one!!"

The main problem is that you need to plan a shutdown and a time-costly
work (nightly ;).

BTW, a workaround (with spares) would be to be able to create a new,
downsized, fs and then migrate content of the old one to the new one.
Steps something like :

 - Have everybody using the old one freeze (hands up!)
 - sync the old fs
 - Move the content of the old fs
 - alias old->new
 - Everybody warm.
 - free space owned by the old fs.

Feasible ?

(ANW, would be helpfull sometime to freeze every process using a fs...)

RN.
IaM




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