Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
/ 2004-04-22 12:17:30 +0530 \ En Chiang Lee: > Is it possible to configure multiple mirrors for a device? The sample > drbd.conf and the documentation seem to indicate that there can only be > one primary and a corresponding secondary. > > If it is possible to have multiple secondaries, what would be the > performance hit in such a config? The performance hit during normal operations would be, well, minimal. latency would probably increase, and we'd need more space for metadata, and/or reorganize it, to keep track of multiple slaves. currently, DRBD replicates to ONE peer, and one peer only. some people on this list made some effort in providing sort of hot spares, i.e. as soon as the current Secondary fails, the Primary starts connecting and syncing to the spare secondary. I think there was a "HA IP" for the DRBD link involved... you have a problem here: we currently only have *one* set of metadata, so we can keep track of one peer only. if the peer changes, to be safe, you need to make a full sync again, even with 0.7. replicating to more than one slave at the same time would need deep support in the structs an logic of the driver. this might be a feature request for DRBD 0.8, though... you could try if software raid on ENBD or something would do what you want, i.e. stacking several layers of virtual device drivers... of course, you also can setup *several* pairs of DRBD, and then put a software raid on top of them. but do not underestimate the administrative complexity, and the logic needed to avoid fubar error scenarios. Lars Ellenberg