The block layers can be layered both ways. DM is the newer infrastructure and was created in the early days of 2.6 If what I was writing could fit into a dm-target, that is what I would do. There are significant projects like drbd and mdraid that are not dm-targets, but I think their is a long term goal to incorporate mdraid's functionality at a minimum into dm. I doubt drbd is ever moved to dm. It is just too big of a project and in use in lots of production server environments. Greg On Tue, May 7, 2013 at 1:46 AM, Gaurav Mahajan <gauravmahajan2007@xxxxxxxxx> wrote: > Hi Neha, > > LVM uses device mapper. Advantages of using device mapper is that you can > stack different dm-targets on each other. > I am really not aware of block device drivers. > > May be Greg can help us understand the actual pros and cons. > > Thanks, > Gaurav > > > On Wed, May 1, 2013 at 9:45 PM, neha naik <nehanaik27@xxxxxxxxx> wrote: >> >> Hi Gaurav, >> I went through your blog and it is really informative. But after reading >> that i realized that i have a question: >> If I want to write a block device driver which is going to sit on lvm >> (and do some functionality on top of it) then should i go for the block >> device driver api >> or write it as a device mapper target. What are the >> advantages/disadvantages of both the approaches. >> >> Regards, >> Neha >> >> >> On Tue, Apr 30, 2013 at 4:24 AM, Gaurav Mahajan >> <gauravmahajan2007@xxxxxxxxx> wrote: >>> >>> Hi Amit, >>> >>> I had compiled some notes on my blog. >>> Here are some links on writing your own device mapper target. >>> http://techgmm.blogspot.in/p/writing-your-own-device-mapper-target.html >>> >>> Concept of device mapper target. >>> http://techgmm.blogspot.in/p/device-mapper-layer-explored-every.html >>> >>> Thanks, >>> Gaurav. >>> >>> >>> On Tue, Apr 30, 2013 at 5:05 AM, Anatol Pomozov >>> <anatol.pomozov@xxxxxxxxx> wrote: >>>> >>>> Hi >>>> >>>> On Mon, Apr 29, 2013 at 9:51 AM, amit mehta <gmate.amit@xxxxxxxxx> >>>> wrote: >>>> > On Sun, Apr 28, 2013 at 5:24 PM, Greg Freemyer >>>> > <greg.freemyer@xxxxxxxxx> wrote: >>>> >> A nice diagram of the overall storage subsystem is at >>>> >> http://www.thomas-krenn.com/en/oss/linux-io-stack-diagram.html >>>> >> >>>> >> Dm is just a single block in it, but it can help to see where it fits >>>> >> in overall. >>>> >> >>>> >> Btw: that diagram doesn't show the legacy ata driver that creates >>>> >> /dev/hdx style devices. Has that been dropped while I wasn't paying >>>> >> attention? I haven't used it in years, but I thought it was still used on >>>> >> embedded systems. >>>> >> >>>> > >>>> > Thank you for sharing the link, but I'm looking for more >>>> > detailed information on I/O stack in Linux, dm-mapper and >>>> > multipath in particular. >>>> >>>> Some docs about multipath can be found here >>>> >>>> http://www.sourceware.org/lvm2/wiki/MultipathUsageGuide >>>> http://christophe.varoqui.free.fr/refbook.html >>>> >>>> The userspace part for tools is here >>>> http://sourceware.org/lvm2/ >>>> >>>> _______________________________________________ >>>> Kernelnewbies mailing list >>>> Kernelnewbies@xxxxxxxxxxxxxxxxx >>>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> >>> >>> >>> _______________________________________________ >>> Kernelnewbies mailing list >>> Kernelnewbies@xxxxxxxxxxxxxxxxx >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies >>> >> > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
