On Thu, Jan 19, 2006 at 09:17:12PM -0500, Phillip Susi wrote: > Neil Brown wrote: > > >Maybe the problem here is thinking of md and dm as different things. > >Try just not thinking of them at all. > >Think about it like this: > > The linux kernel support lvm > > The linux kernel support multipath > > The linux kernel support snapshots > > The linux kernel support raid0 > > The linux kernel support raid1 > > The linux kernel support raid5 > > > >Use the bits that you want, and not the bits that you don't. > > > >dm and md are just two different interface styles to various bits of > >this. Neither is clearly better than the other, partly because > >different people have different tastes. > > > >Maybe what you really want is for all of these functions to be managed > >under the one umbrella application. I think that is was EVMS tried to > >do. > > > > > > > > I am under the impression that dm is simpler/cleaner than md. That > impression very well may be wrong, but if it is simpler, then that's a > good thing. > > > >One big selling point that 'dm' has is 'dmraid' - a tool that allows > >you to use a lot of 'fakeraid' cards. People would like dmraid to > >work with raid5 as well, and that is a good goal. > > > > > > AFAIK, the hardware fakeraid solutions on the market don't support raid5 > anyhow ( at least mine doesn't ), so dmraid won't either. Well, some do (eg, Nvidia). > > >However it doesn't mean that dm needs to get it's own raid5 > >implementation or that md/raid5 needs to be merged with dm. > >It can be achieved by giving md/raid5 the right interfaces so that > >metadata can be managed from userspace (and I am nearly there). > >Then 'dmraid' (or a similar tool) can use 'dm' interfaces for some > >raid levels and 'md' interfaces for others. > > > > Having two sets of interfaces and retrofiting a new interface onto a > system that wasn't designed for it seems likely to bloat the kernel with > complex code. I don't really know if that is the case because I have > not studied the code, but that's the impression I get, and if it's > right, then I'd say it is better to stick with dm rather than retrofit > md. In either case, it seems overly complex to have to deal with both. I agree, but dm will need to mature before it'll be able to substitute md. > > > - > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Regards, Heinz -- The LVM Guy -- *** Software bugs are stupid. Nevertheless it needs not so stupid people to solve them *** =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Heinz Mauelshagen Red Hat GmbH Consulting Development Engineer Am Sonnenhang 11 Cluster and Storage Development 56242 Marienrachdorf Germany Mauelshagen@xxxxxxxxxx +49 2626 141200 FAX 924446 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
