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Date:      Mon, 8 Mar 1999 16:56:59 +1030
From:      Greg Lehey <grog@lemis.com>
To:        Ludwig Pummer <ludwigp@bigfoot.com>, tim@scratch.demon.co.uk, freebsd-questions@FreeBSD.ORG
Subject:   Re: vinum (how to use after creation)
Message-ID:  <19990308165659.U490@lemis.com>
In-Reply-To: <4.1.19990307201038.00a05ee0@mail-r>; from Ludwig Pummer on Sun, Mar 07, 1999 at 08:17:53PM -0800
References:  <4.1.19990307101720.00c13100@mail-r> <199903071254.MAA02531@franklin.matlink> <4.1.19990307101720.00c13100@mail-r> <19990308143012.M490@lemis.com> <4.1.19990307201038.00a05ee0@mail-r>

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On Sunday,  7 March 1999 at 20:17:53 -0800, Ludwig Pummer wrote:
> At 08:00 PM 3/7/99 , Greg Lehey wrote:
>> On Sunday,  7 March 1999 at 10:29:50 -0800, Ludwig Pummer wrote:
>>> At 04:54 AM 3/7/99 , tim@scratch.demon.co.uk wrote:
>>>> I have managed to create some vinum drives as follows
>>> It appears your subdisks are all from the same physical drive. Why would
>>> you do this? Why not just use one usr.p0.s0 with size of 4076?
>>
>> I don't see this.  There's nothing in this list that shows the
>> location of the subdisks, and I assumed he was using a lot of
>> different relatively small disks to get a large volume.  If they *are*
>> all on the same disk, of course, it doesn't make sense, and if the
>> plex were striped, it could cause a terrible loss of performance.
>
> Tim took this onto -chat. I thought he appeared to be using one disk
> because the POs and subdisk sizes perfectly matched...

Yes, they always do with a concatenated plex, unless there is a
subdisk missing.  PO stands for plex offset, which in the case of a
concatenated plex is the starting point of the subdisk in the plex.
In the case of RAID-5 and striped plexes, it's the offset from the
beginning of the plex to the first stripe on that subdisk, so it'll
show increments of stripe size.

> Tim explained that he was experimenting with vinum and ended up with
> all of these small subdisks on one drive.

Ah.  I couldn't know that.

>> Without knowing what he wants to use it for, you can't recommend the
>> 8192 byte blocks.
>
> 8192 byte blocks & 1024 byte frags are the default (at least, according to
> sysinstall, when you choose 'newfs options' from the partition
> editor). 

Hmm.  So they are.  I could have sworn they used to be 4K.  OK, if
they're the default, you don't need to specify them.

Greg
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