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Re: error making real-time filesystem + logging question

Subject: Re: error making real-time filesystem + logging question
From: "D. Stimits" <stimits@xxxxxxxxxx>
Date: Tue, 04 Dec 2001 11:04:40 -0700
Cc: XFS Mailing list <linux-xfs@xxxxxxxxxxx>
References: <E16BJ59-0001TN-00@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> <Pine.LNX.4.30.0112041813080.21659-100000@xxxxxxxxxxxxxxxxx> <20011204112949.U1046@xxxxxxx>
Reply-to: stimits@xxxxxxxxxx
Sender: owner-linux-xfs@xxxxxxxxxxx
Nathan Straz wrote:
> 
> On Tue, Dec 04, 2001 at 06:14:09PM +0100, Roy Sigurd Karlsbakk wrote:
> > On Tue, 4 Dec 2001, Ralf G. R. Bergs wrote:
> >
> > > On Tue, 4 Dec 2001 17:45:35 +0100 (CET), Roy Sigurd Karlsbakk wrote:
> > >
> > > >I'm trying to make a real-time filesystem
> > >
> > > This is from http://oss.sgi.com/projects/xfs/102_caveats.html
> > >
> > > > Realtime volumes not implemented
> > > >
> > > > Realtime volumes are not yet tested in XFS Linux and should not be used.
> > >
> > > I guess that pretty much says it all... :-)
> > ok.. bummer!
> >
> > I really need to increase some sort of chunk size dramatically. Do you
> > know any other way of doing this? I also want the log somewhere else, like
> > on a separate spindle. I may be able to use ReiserFS to do this, but I
> > don't know yet.
> 
> Realtime subvolumes is on my things to test before the next release.  I
> don't know when it will get done, but it will take a bit of test
> development to do it.  Realtime files on XFS require an ioctl, so apps
> will need some work to support them.

Now I'm curious, what's the basic purpose and performance difference
between a real-time filesystem and a "normal" filesystem? Is it some
sort of caching behavior change more suitable for streaming media?

Just curious.

D. Stimits, stimits@xxxxxxxxxx

> 
> To create an external log, you should use something like:
> 
>            mkfs.xfs -l logdev=/dev/sdb1,size=10000b /dev/sda1
> 
> Where /dev/sda1 is your XFS partition and /dev/sdb1 is your log
> partition on a separate spindle.  Adjust size= to fit your application.
> 
> As far as "chunk size" is concerned, you probably want to look at
> something like "-d sunit=,swidth=".  Read more about these in the
> mkfs.xfs man page.
> 
> --
> Nate Straz                                              nstraz@xxxxxxx
> sgi, inc                                           http://www.sgi.com/
> Linux Test Project                                  http://ltp.sf.net/


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