Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On Tue, Jun 14, 2011 at 07:00:03PM +0900, Junko IKEDA wrote: > Hi, > > It is announced that drbd v8.4 supports multiple replicated volumes in > a single DRBD connection, > and I'm really interested in this feature. > > I have no experience of running more than one resource, > we can sync/resync the multi resources using multi ports with drbd 8.3, right? > Is there any problems in this way? > just paining to handle too many ports and the complex setting, > or some performance issue? It is about different replication links failing independently. Imagine you have a data base log on drbd0, and the table space on drbd1. Then, for some reason, first one replication link goes down, and only a bit later the other. On the peer, both will be consistent data, but consistency accross devices is pure luck. Or you do async replication, and one replication link is a bit ahead of the other (for whatever tcp/networking interaction). Then you get a Primary node crash. So you lost some data due to "async". But you also cannot be sure that the write-after-write dependencies _between_ devices are ok. If you pipe both through the same replication link, write dependencies will be ok, even if crossing devices. "async" still loses those updates that have not yet reached the peer. But everything that did reach the peer did so in the "correct order". And similar such scenarios. If you replicate independend data sets, it is ok to mirror them via different replication links. If however your datasets strictly depend on each other, but still live on distinct devices, you really want them to go via the same replication link. Does that help, or did I misinterpret what you have been asking? Lars -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. __ please don't Cc me, but send to list -- I'm subscribed