Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Thank you for your quick response! > Imagine you have a data base log on drbd0, and the table space on drbd1. That's exactly what I am planning to set up. If database team hold firm on separating log and table, I had better to wait drbd v8.4. but, I think they will say "we don't care", so I will use one resource setup with v8.3. and, the explanation for async replication is also informative. Thanks a lot. Thanks, Junko 2011/6/14 Lars Ellenberg <lars.ellenberg at linbit.com>: > 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 > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user >