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>
next in thread | previous in thread | raw e-mail | index | archive | help
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.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20040929230929.GA31474>