Hey there, We've got a prototype version working in-house. We've also implemented a block device client and server. Another client and server could probably be rbd and dm-thin. Will update as soon as we have a github link. Some technical details - Ability to perform sync across storage nodes without the involvement of the client. - This helps performing sync, extending/adding legs/members without the help of the client. Candidate users - We've implemented a stand-alone replicating block device. The client is similar to the rnbd-clt and our own corresponding "store"/server does linear mapping on the server side. - rbd could be a client of rmr-clt. The rmr-srv (store) would talk to lvm. rbd would provide the block device (over multiple objects) on the client side. Lvm would function as the store on the server side. One object would be stored on one dm-thin volume. rmr would provide for the replication in the network. Setups: RMR vs MD-RAID vs DRBD - Active-active - RMR as means of replication over network differs from the md-raid configuration because sync traffic goes directly between servers. The difference to the drbd setup is that the IO traffic goes to both legs in a single hop. How does RMR solve the activity log issue - Synchronous replication; much like Protocol C of DRBD. - RMR tracks all successful queue_depth (max number of IOs that can be inflight at any moment) worth of last IOs on each storage node. Best, Haris Signed-off: alexv.marov@xxxxxxxxx Reviewed-by: danil.kipnis@xxxxxxxxxx On Sun, Nov 22, 2020 at 5:20 PM Danil Kipnis <danil.kipnis@xxxxxxxxxxxxxxx> wrote: > > On Fri, Sep 4, 2020 at 5:33 PM Bart Van Assche <bvanassche@xxxxxxx> wrote: > > > > On 2020-09-04 04:35, Danil Kipnis wrote: > > > On Thu, Sep 3, 2020 at 1:07 AM Bart Van Assche <bvanassche@xxxxxxx> wrote: > > >> How will it be guaranteed that the resulting software does > > >> not suffer from the problems that have been solved by the introduction > > >> of the DRBD activity log > > >> (https://www.linbit.com/drbd-user-guide/users-guide-drbd-8-4/#s-activity-log)? > > > > > > The above would require some kind of activity log also, I'm afraid. > > > > How about collaborating with the DRBD team? My concern is that otherwise > > we will end up with two drivers in the kernel that implement block device > > replication between servers connected over a network. > > Will take a closer look at drbd, > > Thank you, > Danil. > > > > > Thanks, > > > > Bart.
