[linux-lvm] Re: [lvm-devel] [ANNOUNCE] LVM reimplementation ready for beta testing

[Steve Pratt]

Joe Thornber wrote:
>On Wed, Jan 30, 2002 at 10:03:40PM +0000, Jim McDonald wrote:
>> Also, does/where does this fit in with EVMS?

>EVMS differs from us in that they seem to be trying to move the whole
>application into the kernel,

No, not really.  We only put in the kernel the things that make sense to be
in the kernel, discovery logic, ioctl support, I/O path.  All configuration
is handled in user space.

> whereas we've taken the opposite route
>and stripped down the kernel side to just provide services.

Then why does snapshot.c in device mapper have a read_metadata function
which populates the exception table from on disk metadata?  Seems like you
agree with us that having metadata knowledge in the kernel is a GOOD thing.

>This is fine, I think there's room for both projects.  But it is worth
>noting that EVMS could be changed to use device-mapper for it's low
>level functionality.  That way they could take advantage of the cool
>work we're doing with snapshots and pvmove, and we could take
>advantage of having more eyes on the core driver.

Since device_mapper does not support in kernel discovery, and EVMS relies
on this, it would be very difficult to change EVMS to use device_mapper.
Besides, EVMS already has all the capabilities provided by device mapper,
including a complete LVM1 compatibility package.

>LVM2 may not seem that exciting initially, since the first release is
>just concentrating on reproducing LVM1 functionality.  But a lot of
>the reason for this rewrite is to enable us to add in the new features
>that we want (such as a transaction based disk format).  It's on this
>new feature list that we'll be mainly competing with EVMS.

Why compete, come on over and help us :-)

Steve


EVMS Development - http://www.sf.net/projects/evms
Linux Technology Center - IBM Corporation
(512) 838-9763  EMAIL: SLPratt at US.IBM.COM