[linux-lvm] Re: Device-mapper submission for 2.4

Thu Dec 11 14:53:02 UTC 2003

Hi,

Is there a patch for device-mapper for kernel 2.4.23?

Thanks

Yanick

> -----Original Message-----
> From: Alasdair G Kergon [mailto:agk at uk.sistina.com]
> Sent: 11 December, 2003 14:48
> To: linux-kernel at vger.kernel.org; linux-lvm at sistina.com
> Cc: Paul Jakma; Mike Fedyk; Joe Thornber; Marcelo Tosatti; Linus
Torvalds
> Subject: [linux-lvm] Re: Device-mapper submission for 2.4
> 
> On Wed, Dec 10, 2003 at 03:40:07PM -0800, Mike Fedyk wrote:
> > On Wed, Dec 10, 2003 at 05:00:43PM +0000, Paul Jakma wrote:
> > > On Wed, 10 Dec 2003 venom at sns.it wrote:
> > > > DM is back compatible with LVM1, tested and runs well.
> > > What about the patches posted by Joe last (?) week which remove
LVM1
> > > support from 2.6 DM?
> 
> They remove support for the broken version 1 of the device-mapper
> ioctl interface.  This is nothing to do with LVM1.
> 
> > If this is what I was reading being discussed a few weeks ago, then
the
> > support for the LVM1 sysctls/ioctls has/will be removed, so you will
> have to
> > use the DM utilities instead of the old LVM1 utilities.  LVM1
on-disk
> format
> > should still be supported.
> 
> 2.6 does not support LVM1 ioctls.
> LVM2 userspace tools and EVMS both support LVM1 on-disk format using
> device-mapper.
> 
> 
> Here's a reference sheet to help clarify the terminology and explain
> what's happening.
> 
> LVM1 = Userspace tools + kernel ioctls included in marcelo's 2.4 tree
>   - LVM1 kernel ioctls are *not* included in or available for 2.6
>   - LVM1 userspace tools do *not* work with 2.6 kernels
> 
> dm = Kernel driver (GPL) for new volume managers to use.
>   - Included in Linus's 2.6 kernels.
>   - Available as a patch for 2.4 kernels from the Sistina website.
>   - Knows *nothing* about volume manager's on-disk metadata layouts.
>   - Userspace volume managers (e.g. EVMS and LVM2) communicate via a
new
>     ioctl interface.
>   - This ioctl interface is currently "version 4" and we regard it as
>     stable.  [Some enhancements are on the horizon, but nothing that
>     breaks existing code/binaries.]
>   - An old development version of this device-mapper ioctl interface
known
>     as "version 1" has problems with it, is deprecated and should be
>     removed from kernel trees ASAP.
>     Always use "version 4" when building new kernels today.
> 
> libdevmapper = Userspace shared library (LGPL) which wraps a volume
> manager
>                application interface around the device-mapper ioctls
>   - Can determine transparently whether the kernel device-mapper is
using
>     "version 4" dm ioctl interface or the deprecated "version 1"
interface
>     and adapt itself accordingly.  [configure --enable-compat]
>   - Can only communicate with device-mapper: it cannot use LVM1
ioctls.
>   - Designed primarily for use by LVM2 tools.  [EVMS does not use it]
>   - Some parts of the libdevmapper API are not yet stable and are
likely
>     to get changed.
> 
> dmsetup = Userspace utility (GPL) which provides full command-line
access
> to
>           the libdevmapper API.
>   - Designed for use by shell scripts and for testing and debugging.
>   - Command line interface may be considered stable.  New features may
get
>     added, but we'll try not to break existing commands.
> 
> LVM2 = New Logical Volume Manager command line tools (GPL) designed to
>        be backward-compatible with LVM1 and offering new features and
>        more flexibility, configurability and stability.
>   - Supports existing LVM1 on-disk metadata.
>     This means you do *not* have to make changes to your existing
on-disk
>     LVM1 volumes to switch between using LVM1 and LVM2.
>   - Uses command lines similar to LVM1.
>   - By default uses a new on-disk metadata format supporting more
>     features than the original LVM1 version.
>   - Communicates with the device-mapper kernel driver via
libdevmapper's
>     API.
> 
> 
> Miscellaneous points:
>   - LVM1 uses block major number 58: dm selects one or more major
numbers
>     dynamically as required instead.
>   - LVM1 uses character major number 109: dm selects a misc minor
number
>     dynamically instead.
>   - There's a (non-devfs) script for creating /dev/mapper/control at
>     startup (or after dm module load).
>   - You can use LVM1 tools with unpatched 2.4 kernels.
>   - You can use LVM2 tools with patched 2.4 and unpatched 2.6 kernels.
>   - Device-mapper support for snapshots and pvmove is so far released
>     only for 2.4.  Patches for 2.6 are being tested.
>   - Multipath and mirror support are under development for 2.6.
>     (Then get back-ported to 2.4.)
> 
> Web download page: http://www.sistina.com/products_lvm_download.htm
> 
> The device-mapper tarball contains:
>   device-mapper kernel patches - needed only for 2.4;
>   userspace libdevmapper and dmsetup - needed with all dm kernels.
> The LVM2 tarball contains the LVM2 command line tools.
> 
> Development code can be found via:
>   http://people.sistina.com/~thornber/  (for kernel patches)
>   http://www.sistina.com/products_CVS.htm  (for userspace code)
> 
> Device-mapper mailing list:
>   http://lists.sistina.com/mailman/listinfo/dm-devel
> 
> Alasdair
> --
> agk at uk.sistina.com
> 
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