On Sun, Aug 12, 2007 at 01:35:17PM +0300, Al Boldi (a1426z@xxxxxxxxx) wrote: > Lars Ellenberg wrote: > > meanwhile, please, anyone interessted, > > the drbd paper for LinuxConf Eu 2007 is finalized. > > http://www.drbd.org/fileadmin/drbd/publications/ > > drbd8.linux-conf.eu.2007.pdf > > > > it does not give too much implementation detail (would be inapropriate > > for conference proceedings, imo; some paper commenting on the source > > code should follow). > > > > but it does give a good overview about what DRBD actually is, > > what exact problems it tries to solve, > > and what developments to expect in the near future. > > > > so you can make up your mind about > > "Do we need it?", and > > "Why DRBD? Why not NBD + MD-RAID?" > > Ok, conceptually your driver sounds really interresting, but when I read the > pdf I got completely turned off. The problem is that the concepts are not > clearly implemented, when in fact the concepts are really simple: > > Allow shared access to remote block storage with fault tolerance. > > The first thing to tackle here would be write serialization. Then start > thinking about fault tolerance. > > Now, shared remote block access should theoretically be handled, as does > DRBD, by a block layer driver, but realistically it may be more appropriate > to let it be handled by the combining end user, like OCFS or GFS. > > The idea here is to simplify lower layer implementations while removing any > preconceived dependencies, and let upper layers reign free without incurring > redundant overhead. > > Look at ZFS; it illegally violates layering by combining md/dm/lvm with the > fs, but it does this based on a realistic understanding of the problems > involved, which enables it to improve performance, flexibility, and > functionality specific to its use case. > > This implies that there are two distinct forces at work here: > > 1. Layer components > 2. Use-Case composers > > Layer components should technically not implement any use case (other than > providing a plumbing framework), as that would incur unnecessary > dependencies, which could reduce its generality and thus reusability. > > Use-Case composers can now leverage layer components from across the layering > hierarchy, to yield a specific use case implementation. > > DRBD is such a Use-Case composer, as is mdm / dm / lvm and any fs in general, > whereas aoe / nbd / loop and the VFS / FUSE are examples of layer > components. > > It follows that Use-case composers, like DRBD, need common functionality that > should be factored out into layer components, and then recompose to > implement a specific use case. Out of curiosity, did you try ndb+dm+raid1 compared to drbd and/or zfs on top of distributed storage (which is a urprise to me, that holy zfs suppors that)? > Thanks! > > -- > Al > > - > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Evgeniy Polyakov - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
