Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
So activity log is used only when two nodes are connected ? I believe SRL in VVR stores the IO write order, so it may contain serval writes to a same block. On Wed, Sep 21, 2011 at 8:35 PM, Felix Frank <ff at mpexnet.de> wrote: > Hi, > > good question. > > On 09/21/2011 12:23 PM, Lyre wrote: >> Hi all: >> >> DRBD background resync doesn't promise the IO write order, is that right ? >> >> However, when would actitivy log take effect? In my opinion, it is >> similiar to SRL in VVR. But I'm confused, I'm curious how does it >> work. >> >> Considering this situtaion: >> >> Oracle runs on Primary node (node1) , while secondary node (node2) disconnected. >> >> when I connect the drbd on node2, the background resync begin. If >> node crashed during background sync, could it be possible to bring the >> oracle up no node2? Or is there a way to keep the secondary >> consistent? SRL in VVR was able the keep the IO write order. > > I'm not familiar with that technology, but with DRBD, this cannot work. > > The problem isn't with write order alone. If a block is written multiple > times, the data of the earlier writes is lost. DRBD won't keep some sort > of stash and keep several revisions for single blocks (imagine the cost!). > > So no - whenever a resync becomes necessary, you are faced with an > inconsistent SyncTarget as long as the sync is not completed. > DRBD won't allow you to access this data, which is the only sane thing > to do, really. > > HTH, > Felix >