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Re: Map a disk LBA to filename?

To: Carsten Aulbert <carsten.aulbert@xxxxxxxxxx>
Subject: Re: Map a disk LBA to filename?
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 28 Oct 2008 18:21:05 +1100
Cc: Michal Soltys <nozo@xxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <4906BB32.8080403@xxxxxxxxxx>
Mail-followup-to: Carsten Aulbert <carsten.aulbert@xxxxxxxxxx>, Michal Soltys <nozo@xxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
References: <4905A3FB.6080709@xxxxxxxxxx> <20081027114945.GE4985@disturbed> <4905B48A.8010108@xxxxxxxxxx> <4905BC13.3030402@xxxxxxxxxxxxxx> <20081027233516.GG4985@disturbed> <4906BB32.8080403@xxxxxxxxxx>
User-agent: Mutt/1.5.18 (2008-05-17)
On Tue, Oct 28, 2008 at 08:11:46AM +0100, Carsten Aulbert wrote:
> Hi Dave et al
> Dave Chinner wrote:
> > Blockget - yes it will. It just does the traversal internally to
> > build the mapping. With large filesystems xfs_db can run out of
> > memory building the mapping, which is why I've used the
> > explicit traverse+xfs_bmap method in the past....
> How expensive is this operation (rule of thumb)? We will mostly use this
> on compute nodes where the partition is 500-750 GB large and the node
> has 8 GB of memory. For the simple test where I apparently hit thin air
> I have not seen anything bad in terms of memory consumption.

Shouldn't be a problem with a filesystem that size. It's when you're
dealing with tens of terabytes in a single filesystem that it can
be a problem...


Dave Chinner

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