Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Hi, > > > > > > I guess one of the reasons to have this option is for users upgrading from a > > previous drbd version (<0.7.0) to >= 0.7.0. > > E.g. people having a drbd-0.6 device will have a problem upgrading to 0.7.x > > since drbd now needs 128MB of metadata on the underlying device and so one > > would be forced to shrink the filesystem. As you might guess fs shrinking is > > always pretty dangerous. So setting up the meta data anywhere else might be > > the only solution in those cases. > > even though we do our best to reduce meta-data updates, > which are additional small synchronouse writes generated within the > applications (file systems) write-out path, they do occur. > > if you have a large device with internal meta data, this involves > seeking from the active set somewhere to the very end of the device, > and back again. In our case, the disk itself is only 73GB, and the DRBD partition is only 40GB, and the the machine is mainly acting as a web server, so large numbers of writes are not likely to be an issue. > if you put it on a separate (physical!) device, this is not an issue. > > also, if you put the meta data on a differen (this time it may even be > logical) device, then resizing the drbd device later will be much less > cumbersome, and less risky, too. unfortunately they are also easier to > mix up, if you reconfigure frequently. drbdadm just believes its config > file. there is not too much paranoia in place to avoid the admin to > shoot himself. Yes - I can see how added complexity could also add to the potential for an admin stuff up In the case of migrating an existing DRBD device to a new disk (e.g., if you needed to move to a larger disk), could you use a utility like 'tar' to back the DRBD device up, configure the new DRBD device, and then tar the data back? Will this cause problems with meta-data from the old device? I am guessing that 'tar' and 'cp' (what about 'dump') won't see it as it not part of the filesystem as such... Out of curiosity, how is the meta-data itself stored when it is 'internal'? > > > all the documentation (as far as I can see), but am not really sure > > > which is more suitable. It mentions in the documentation that if you > > > use meta-data internal, then you should 'shrink an existing filesystem > > > first'. I'm not sure what this means. The main reason behind my question > > > > 3. if you really screw up, and you feel the need to fiddle with the drbd > meta data, there is a write_gc.pl script ... > but you should understand the details of the drbd GCs, and double > check that script, before you use it. I can't see myself wanting to do that anytime soon. Thanks for your time in filling in some of the blanks here! Regards, Campbell > please use the "List-Reply" function of your email client. > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user