Date: Wed, 29 Sep 2004 19:09:29 -0400 From: David Schultz <das@FreeBSD.ORG> To: Nehal <nehalmistry@gmx.net> Cc: freebsd-fs@FreeBSD.ORG Subject: Re: data blocks question Message-ID: <20040929230929.GA31474@VARK.MIT.EDU> In-Reply-To: <20040929154328.00001444@nehal> References: <20040929101403.000027aa@nehal> <20040929204233.GB30629@VARK.MIT.EDU> <20040929154328.00001444@nehal>
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On Wed, Sep 29, 2004, Nehal wrote: > On Wed, 29 Sep 2004 16:42:33 -0400 > David Schultz <das@FreeBSD.ORG> wrote: > > > On Wed, Sep 29, 2004, Nehal wrote: > > > on my ufs2 partition, there is a file that has a size of > > > 65536, and has 2 direct blocks only. the block size of the fs > > > is 16k and fragment block size is 2k. > > > > > > how can this be possible? wouldn't 2 direct blocks mean that > > > the maximum size is 2x16k = 32k? or am i not understanding > > > something correctly? > > > > > > i've made a copy of the file, and the new file has 4 direct > > > blocks. > > > > > > it is a binary file, and i can read it fine (ie, cat it). i've > > > done fsck on the filesystem and it found no problem. > > > > Yes, UFS supports sparse files. That is, you can have a file > > with parts you haven't written to, and the blocks for those > > parts won't be allocated. The cp utility doesn't know about > > this, though, so copies will have the ``holes'' filled with > > zeroes. > > > > how would i determine the offset and length of these 'holes' for > sparse files? It's an implementation detail, so you're not supposed to need to know most of the time. You can use fsdb to find out.home | help
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