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Date:      Tue, 13 Feb 2007 10:27:11 +0100 (CET)
From:      Oliver Fromme <olli@lurza.secnetix.de>
To:        freebsd-fs@FreeBSD.ORG, randy@psg.com, nesimi@yahoo.com
Subject:   Re: comments on newfs raw disk ?  Safe ? (7 terabyte array)
Message-ID:  <200702130927.l1D9RBn9034761@lurza.secnetix.de>
In-Reply-To: <17873.33060.746546.773210@roam.psg.com>

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Randy Bush wrote:
 > this has been a wonderfully well-timed thread as i am about
 > to hack a 4tb array tomorrow afternoon.  the normal spindle
 > is separate and partitioned to death and newfsed using the
 > defaults.  with 2gb of ram, i figure 6gb swap just in case
 > two userland hogs are running at once, e.g. some hog while
 > background fsck is running.

A bit careful here ...  Background fsck had some issues,
especially when the machine crashed or is otherwise reset
while the background fsck is still running.  It resulted
in corruption that could not be repaired by fsck anymore.
I don't know if all of those issues have been resolved in
RELENG_6, but personally I always disable background fsck
on all of my machines, just to be safe.

Also note that background fsck will take longer than regular
fscp, and it puts more stress on the disk, depending on
what kind of applications run at the same time.

 > the 4tb will be used as a dump/restore target only.  so i
 > am thinking few files, relatively big ones, little i/o and
 > more write than read.
 > 
 > so my current plan is
 > 
 > newfs  -b 16384 -f 2048 -i 262144
 > 
 > i would crank up even further, but these are the largest
 > numbers mentioned in tuning(7).
 > 
 > i will leave -m alone for now.
 > 
 > does this seem reasonable?

Yes, I think so.  I would probably use the very same numbers
in that case.  I've also heard of people using 1 MB per
inode (-i 1048576), but I haven't tried that high a number
myself.  -i 262144 works fine.

In a thread some time ago, Matt Dillon commented on very
high -i numbers:

Matt Dillon wrote:
 > [...]
 > :> newsfeed-inn# newfs -i 67108864 /dev/twed0d
 > :> [stuff deleted]
 > :> 1048576032, 1048641568, 1048707104, 1048772640, 1048838176, 1048903712,
 > :> 1048969248, 1049034784, 1049100320, 1049165856, 1049231392, 1049296928,
 > :> 1049362464, 1049428000, 1049493536, 1049559072, 1049624608, 1049690144,
 > :> 1049755680, 1049821216, 1049886752, 1049952288, 1050017824, 1050083360,
 > :> 1050148896, 1050214432, 1050279968, 1050345504, 1050411040, 1050476576,
 > :> 1050542112, 1050607648, 1050673184, 1050738720, 1050804256, 1050869792,
 > :> 1050935328
 > :> fsinit: inode value out of range (2).
 > :>
 > :> Tried larger -i parameters, same thing.
 > :>
 > :> Can't newfs figure this out before it gets to this point that something
 > :> isn't going to work?
 > :>
 > :> I'll try some different block/frag sizes, see if it helps.
 > 
 >     Specifying a byte-to-inode ratio that large is kind of silly.  I
 >     usually use something like -i 262144 -b 16384 -f 2048 on my larger
 >     filesystems.  A couple of million would also probably work, but beyond
 >     that you aren't really saving anything, not even fsck time.  I'm not
 >     surprised that 67 million doesn't work.
 > 
 >                                                 -Matt

Best regards
   Oliver

-- 
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
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secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün-
chen, HRB 125758,  Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart
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