Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
> Do you have any tip about choosing between a primary/secondary and primary/primary drbd configuration? > > I mean, thinking about a simple disaster recovery setup. In other words: > A small environment with just two servers. One is working while the other sleeps and mirrors drbd blocks. > If primary deads, secondary will be started. > > In my logic, this should fit a drbd primary/secondary setup. > > But then some questions are arising in my mind, and they are common tasks in the everyday production life: > - for some reason I must turn off the main server for maintenance. It will be set drbd secondary and shut down and for some hours the work will be done by the server2. Well. When is time to switch back... What is the best practice to pretty well syncronize the new datas that have been written on server2's drbd? > Should I set server2 drbd secondary? (I don't think so) > Is drbd managing automatically the difference? (i.e. simply setting back server1 drbd primary) > Or I should beware about some correct steps to be done? > > In other words I can't find some everyday scenarios and practical cases/practices in drbd online user guide. > > I'd really thank you so much if you have some tip/guidelines (or maybe also some web lins) to help me with that question, because it also matches the scenario where server1 really dies. > > Thank you for reading too. > > Kind regards > Roberto > This is the type of question you should ask on the list. I may get it wrong<g>, or someone else may have a better answer. I'm assuming you are not using a heartbeat or pacemaker setup, and are not using a cluster-aware file system and intend to fail over to the stand-by box manually. If those assumptions are incorrect, please let us know. Following a failure of the primary, the secondary should be in WFConnection and hopefully in UpToDate/Unknown status. If so, on the secondary simply drbdadm primary <resource>, mount the filesystem, and start the applications. After the primary is repaired, drbd should rebuild the disks to match. To fail back to the original machine, use the procedure below, reversing primary and secondary. For scheduled maintenance (ie, a planned outage) do this: On the primary: Stop the applications unmount the filesystem stop drbd (or drbdadm secondary <resource>, if failing back) shutdown (unless failing back) On the secondary: drbdadm primary <resource> mount the filesystem start the applications When reestablishing the connection, the disks should automatically resynchronize. If they do not, the reason will be in the logs. Rectify the reason and primary, mount, start. Dan