On 7/31/07, Evgeniy Polyakov <johnpol@xxxxxxxxxxx> wrote: > Hi. > > I'm pleased to announce first release of the distributed storage > subsystem, which allows to form a storage on top of remote and local > nodes, which in turn can be exported to another storage as a node to > form tree-like storages. Very interesting work, I read through your blog for the project and it is amazing how quickly you developed/tested this code. Thanks for capturing the evolution of DST like you have. > Compared to other similar approaches namely iSCSI and NBD, > there are following advantages: > * non-blocking processing without busy loops (compared to both above) > * small, plugable architecture > * failover recovery (reconnect to remote target) > * autoconfiguration (full absence in NBD and/or device mapper on top of it) > * no additional allocatins (not including network part) - at least two in > device mapper for fast path > * very simple - try to compare with iSCSI > * works with different network protocols > * storage can be formed on top of remote nodes and be exported > simultaneously (iSCSI is peer-to-peer only, NBD requires device > mapper and is synchronous) Having the in-kernel export is a great improvement over NBD's userspace nbd-server (extra copy, etc). But NBD's synchronous nature is actually an asset when coupled with MD raid1 as it provides guarantees that the data has _really_ been mirrored remotely. > TODO list currently includes following main items: > * redundancy algorithm (drop me a request of your own, but it is highly > unlikley that Reed-Solomon based will ever be used - it is too slow > for distributed RAID, I consider WEAVER codes) I'd like to better understand where you see DST heading in the area of redundancy. Based on your blog entries: http://tservice.net.ru/~s0mbre/blog/devel/dst/2007_07_24_1.html http://tservice.net.ru/~s0mbre/blog/devel/dst/2007_07_31_2.html (and your todo above) implementing a mirroring algorithm appears to be a near-term goal for you. Can you comment on how your intended implementation would compare, in terms of correctness and efficiency, to say MD (raid1) + NBD? MD raid1 has a write intent bitmap that is useful to speed resyncs; what if any mechanisms do you see DST embracing to provide similar and/or better reconstruction infrastructure? Do you intend to embrace any exisiting MD or DM infrastructure? BTW, you have definitely published some very compelling work and its sad that you're predisposed to think DST won't be recieved well if you pushed for inclusion (for others, as much was said in the 7.31.2007 blog post I referenced above). Clearly others need to embrace DST to help inclusion become a reality. To that end, its great to see that Daniel Phillips and the other zumastor folks will be putting DST through its paces. regards, Mike - 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
