From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?iso-8859-1?Q?Ragnar_Kj=F8rstad?= Subject: Re: [linux-lvm] offtopic but ... Message-Id: <20020508182151.I18743@vestdata.no> References: <20020508082357.B18631@connectlive.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: ; from jovi@unixag-zw.fh-kl.de on Wed, May 08, 2002 at 04:12:48PM +0200 Content-Transfer-Encoding: quoted-printable Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: Date: Wed May 8 11:20:02 2002 List-Id: Content-Type: text/plain; charset="iso-8859-1" To: linux-lvm@sistina.com On Wed, May 08, 2002 at 04:12:48PM +0200, Oliver Jovic wrote: > application > | > +---------------------------------------------------------------------- > | > | virtual device > | > +---------------------------------------------------------------------- > | | | | > +----------+ +----------+ +----------+ +----------+ > | | | | | | | | > | /dev/hda | | /dev/hdb | | /dev/hdc | | /dev/hdd | > | ext3 | | reiserfs | | xfs | | ext2 | > +----------- +----------+ +----------+ +----------+ > index file =3D=3D index file There are many functions you loose if multiple seperate filesystems are used. e.g: what do you do when a file grow to no longer fit on it's original disk? You can not easily move it (atomicly), and you can not easily split it into multiple chunks. If you don't need this functionality, the closest approximation to what you want is a symlink-three. Basicly you can create a very small filesystem with symlinks for each and every file on your "virtual filesystem" (don't call it a virtual device, because that's something different :) ). You can use raid to get redundancy for the link-three, and as it is very small you don't loose a lot of space. You could extend this scheeme to implement a small kernel-module that did : * open("/mnt/hdX/file", O_CREATE) * symlink("/mnt/hdX/file", "/mnt/virtual/file") when your application does * open("/mnt/virtual/file", O_CREATE) to make it more seemless. However, it's once you want it to be totally transparrent, and files to migrate to the disk with more space that it gets complicated. --=20 Ragnar Kj=F8rstad Big Storage