On 2011-09-23 10:09, Lyre wrote: > Hi all: > > Want to know the sync data size of DRBD. > > If application write 1 bytes to a drbd device, how may datas will be > write to another node? In this 2 scenarios: > > 1. Both nodes are connected (UpToDate/UpToDate).
Whatever the minimum chunk is that your application writes do the block device. If you have, say, a block based filesystem such as ext3, and your block size is set to 4K, then the block device is always going to be written to in blocks of 4K. And DRBD will replicate that. That is nothing within DRBD's control though. If you have an application (or filesystem) that writes to its block device in smaller increments, then DRBD will happily replicate those smaller increments too. It's generally a fairly safe bet, though, that filesystems won't attempt to write chunks of data that are smaller than the hard sector size of the underlying physical block device (normally either 512 bytes or 4K). > 2. background resync. Increments of 4K. > In a oracle case, we have file size increased about 135MB, but DRBD > have to transmit about 1GB, is that something wrong? Eh, what? How did you arrive at those numbers, IOW, what makes you think DRBD is transmitting 1G, and in what context? And also, do you have a name? It's rather uncommon on this last to post from a non-identifiable GMail address and also to never give one's name in a signature. Cheers, Florian
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