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Date:      Thu, 09 Jun 2005 09:46:03 +0100
From:      Alex Zbyslaw <xfb52@dial.pipex.com>
To:        Frantisek Rysanek <Frantisek.Rysanek@post.cz>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: Summary: 12TB GEOM stripe, newfs, then fsck: cannot alloc 768053748 bytes for blockmap
Message-ID:  <42A801CB.20604@dial.pipex.com>
In-Reply-To: <42A7FAD3.5051.98EB5B15@localhost>
References:  <42A717EB.8095.9574FF2F@localhost> <42A7FAD3.5051.98EB5B15@localhost>

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Frantisek Rysanek wrote:

>Thanks a lot to Mr. Zbyslaw.
>  
>
You're welcome.

>A local friend has suggested to increase the block size to 
>newfs, or something along those lines - essentially to
>decrease the FS overhead and the size of the "blockmap".
>I haven't tried that but I guess it sounds reasonable
>- may make sense on machines where you just can't get
>enough RAM or are not willing to grant it all to a single
>process.
>  
>
It ought also make sense if you are serving up *large* files (didn't you 
say video/audio?).  I'm planning to do some tests at some point to see 
what difference different block/fragment sizes make to performance, but 
haven't found the time yet.  I don't have anything on your scale (23Gb 
of document database pales into insignificance against 12Tb :-) ) but I 
haven't found any specific numbers anywhere.

If you're interested, check out the -b and -f options to newfs.  The 
defaults are 16k/2k.  Decreasing the number of inodes would definitely 
make sense (see -i).  The -N option ought to show you what would happen 
without actually doing anything.

--Alex




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