Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
Am Sonntag, 6. Februar 2005 19:13 schrieb Martin Green: > Hi > > I am exploring the use of DRBD as a backup system for some servers. > So far I've installed it on a couple of test servers, and it's worked > well - > once I understood some idiosynchrasies of the command line :) > Hints would be helpful ;) [...] > I have figured out a number of creative solutions to this: > > - Run DBRD on top of LVM > > - Run Ext3Cow (copy-on-write filesystem) on top of DRBD > > - Run DRBD on top of cowloop (a copy-on-write block driver) > > > But there's a snag with each of them: > > - LVM seems inefficient if you add multiple snapshots > - Ext3Cow has no way of deleteing snapshots > - DRBD won't actually load on top of cowloop ... > What exactly do you mean by "LVM seems inefficient". You can set the chunksize of the snapshot when taking it... they are read/writable... I like LVM2's snapshots... > > I guess I should say that this is largely an experimental endeavour - > if I can make it work, it would solve a problem, but I am also > just curious about what's possibe. > > > So.. I have some questions: > > > How to take backups of the secondary ? [...] > This is my approach: > > - Disconnect DRDB > - Change beta to primary > - Mount it > - Make a backup > - Unmount > - Change it back to secondary > - Reconnect > > It this correct? This would produce a bad mess... Since this looks like a split brain situation to DRBD. Disconnect ; mount it in read-only mode ; reconnect would be better! [...] > I tried exactly this case, copying a 100mb file, then reconnecting. I > then > immediate ran cat /proc/dbrd - but it did not show sync in progress. Hmm ? As long as the "ap:" value in /proc/drbd is greater than zero there is some data in flight... [...] > How does DRBD decide which way to Sync? > ---------------------------------------------------------------- > > Just curious... > > Imagine the scenario above again, but this time I write sectors to both > drives while disconnected. > > How does DRBD decide which one is primary? If I make one secondary > before the reconnect, does it assume that one is to be overwritten? > > I guess I should try it out... See http://www.drbd.org/fileadmin/drbd/publications/drbd_paper_for_NLUUG_2001.pdf > Finally - has anyone patched DBRD to include snapshots? Or is this a > possible future feature? > I use DRBD on top of LVM, so I take the snapshot off the LV and do the backup... No need to disconnect it... -Philipp -- : Dipl-Ing Philipp Reisner Tel +43-1-8178292-50 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Schönbrunnerstr 244, 1120 Vienna, Austria http://www.linbit.com :