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Date:      Thu, 05 Feb 1998 07:21:15 -0600 (CST)
From:      Chris Dillon <cdillon@inter-linc.net>
To:        (Satoshi Asami) <asami@cs.berkeley.edu>
Cc:        freebsd-fs@FreeBSD.ORG
Subject:   Re: May have pounced on something weird with ccd and newfs  (rat
Message-ID:  <XFMail.980205073143.cdillon@inter-linc.net>
In-Reply-To: <199802041558.HAA04258@silvia.HIP.Berkeley.EDU>

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On 04-Feb-98 Satoshi Asami wrote:
>
> * > * I=128     newfs -b 8192 -f 1024 fails with "write error: 2047871
> * > *                                             wtfs: invalid argument".
>
> * I'm not quite sure what you mean by "old" disklabel, but I started out
>fresh
> * with these drives, and labeled them symmetrically with using ccd's in
>mind..
>
>What I meant is if you edit the disklabel on a ccd at a certain
>interleave, the label will "stick" when you later reconfigure the ccd
>with a different interleave (since the disklabel exists in the first
>sector of the first partition).

Aaaah, so maybe the best thing for me to do would have been to throw some zeros
to the front of the partitions I was going to use for the ccd before I
configured it?  Or would it have been enough to throw some zeros onto the ccd
*after* i configured it?

>Since the interleaves are increasing in your test order, it's possible
>that the last few blocks that the disklabel says exist may not exist.

Makes sense, now.

> * Here's the labels for sd0, sd1, and ccd0, and the output of ccdconfig -g.
>
>You are missing the output of ccdconfig -g.  I can't diagnose the
>problem without it.

Whoops. I won't paste the rest of it since its back in this thread somewhere.
:-)

root@cheetah [/root] # ccdconfig -g
ccd0            64      0       /dev/sd0s1g /dev/sd1s1g
ccd1            64      0       /dev/sd0s1h /dev/sd1s1h


> * root@cheetah [/root] # disklabel ccd0
>
> * sectors/unit: 2047872
>
>See the number above (the error from wtfs).  It is second from the
>last block, which could be invalid at a 128 interleave.
> * 3 partitions:
> * #        size   offset    fstype   [fsize bsize bps/cpg]
> *   a:  1023936        0    4.2BSD     1024  8192     0   # (Cyl.    0 -
>499*)
> *   b:  1023936  1023936    4.2BSD     1024  8192     0   # (Cyl.  499*-
>999*)
> *   c:  2047872        0    unused        0     0         # (Cyl.    0 -
>999*)
>
>So you do have a disklabel.  (The ccd driver will return a "default"
>label with only partition "c" and type "4.2BSD" if you don't write one
>yourself...that is often good enough, there usually is no point in
>sub-partitioning the ccd if you're combining disks is the first
>place. :)

When I did the testing, i didn't label the ccd, i let it use the 'c' partition. 
However, i am now using two ccd's, one is using 'c', the other is split with 'a'
and 'b'.  This was more or less a learning thing for me, since I had never set
up any ccd's before, and I wanted to see what kind of performance enhancement I
would get from it.


--- Chris Dillon
--- cdillon@inter-linc.net
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    for Intel x86 based computers (and soon Sparcs).
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