Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Thanks guys for the information. That's exactly what I need. On Wed, Apr 20, 2016 at 3:20 PM, Digimer <lists at alteeve.ca> wrote: > On 20/04/16 02:15 PM, akan tortz wrote: > > Hi ALL, > > > > I’m new to DRBD. > > The goal is to have an asynchronous replication once or twice a day > > between the nodes. > > > > Is this possible with DRBD without DRBD proxy solution? > > > > From what I’ve tested I see that the secondary node can be in a > > disconnected state (drbdadm disconnect <resource>) but I don’t know how > > long. > > Another concern is how much changes (writes) can accommodate the primary > > node while the secondary is offline? Protocol A states that the local > > writes are completed once the local disk write is finished and the > > replication packet is placed in the local TCP send buffer. So that means > > if TCP send buffer is full then DRBD will block all write operations? > > > > Thanks. > > The peer can be disconnected as long as you want. As inodes change, > they're marked dirty (oos:X in /proc/drbd). When the peer connects, it > starts copying those dirty blocks over at the resync rate (dynamic on > 8.4, generally <30% of available performance *at most*). At worst, all > inodes eventually change and the full device needs to be resynced. > > The protocols determine how changes are handled in a connected state > (replication, as opposed to resync). Replication always goes as fast as > possible (maximum write speed less what is being consumed during a > resync operation). The protocol determines when DRBD will report the > write complete to the upper level application. In protocol A, that > happens as soon as the data is on the outbound network buffer. Protocol > C waits until the peer confirms the data made it to persistent storage. > Thus, Protocol A is async replication where protocol C is sync replication. > > When the peer is disconnected, no replication is attempted so the > protocol has no meaning. The inode(s) are marked dirty and it's done. > > -- > Digimer > Papers and Projects: https://alteeve.ca/w/ > What if the cure for cancer is trapped in the mind of a person without > access to education? > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linbit.com/pipermail/drbd-user/attachments/20160420/152c1df3/attachment.htm>