On 2020-09-09 04:42, Danil Kipnis 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. > > I have two general understanding questions: > - What is the conceptual difference between DRBD and an md-raid1 with > one local leg and one remote (imported over srp/nvmeof/rnbd)? I'm not sure there is a conceptual difference. But there will be a big difference in recovery speed after a temporary network outage (assuming that the md-raid write intent bitmap has been disabled). > - Is this possible to setup an md-raid1 on a client sitting on top of > two remote DRBD devices, which are configured in "active-active" mode? I don't think that DRBD supports this. From the DRBD source code: "this code path is to recover from a situation that "should not happen": concurrent writes in multi-primary setup." Bart.
