Hello, just as a small addition: The numbers also depend on your consistency level used for reads. It will behave like that if you just read on local nodes. If you do reads on ALL, QUORUM or EACH_QUORUM etc. you need also include the read volume in the calculation.
Regards, Georg Am Mi., 15. Jan. 2020 um 19:35 Uhr schrieb Osman Yozgatlıoğlu < osman.yozgatlio...@gmail.com>: > Thank you. I have an insight now. > > Regards, > Osman > > On Wed, 15 Jan 2020 at 19:18, Reid Pinchback <rpinchb...@tripadvisor.com> > wrote: > > > > Oh, duh. Revise that. I was forgetting that multi-dc writes are sent > to a single node in the other dc and tagged to be forwarded to other nodes > within the dc. > > > > So your quick-and-dirty estimate would be more like (write volume) x 2 > to leave headroom for random other mechanics. > > > > R > > > > > > On 1/15/20, 11:07 AM, "Reid Pinchback" <rpinchb...@tripadvisor.com> > wrote: > > > > Message from External Sender > > > > I would think that it would be largely driven by the replication > factor. It isn't that the sstables are forklifted from one dc to another, > it's just that the writes being made to the memtables are also shipped > around by the coordinator nodes as the writes happen. Operations at the > sstable level, like compactions, are local to the node. > > > > One potential wrinkle that I'm unclear on, is related to repairs. I > don't know if merkle trees are biased to mostly bounce around only > intra-dc, versus how often they are communicated inter-dc. Note that even > queries can trigger some degree of repair traffic if you have a usage > pattern of trying to read data recently written, because at the bleeding > edge of the recent changes you'll have more cases of rows not having had > time to settle to a consistent state. > > > > If you want a quick-and-dirty heuristic, I'd probably take (write > volume) x (replication factor) x 2 as a guestimate so you have some > headroom for C* and TCP mechanics, but then monitor to see what your real > use is. > > > > R > > > > > > On 1/15/20, 4:14 AM, "Osman Yozgatlıoğlu" < > osman.yozgatlio...@gmail.com> wrote: > > > > Message from External Sender > > > > Hello, > > > > Is there any way to calculate inter dc bandwidth requirements for > > proper operation? > > I can't find any info about this subject. > > Can we say, how much sstable collected at one dc has to be > transferred to other? > > I can calculate bandwidth with generated sstable then. > > I have twcs with one hour window. > > > > Regards, > > Osman > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org > > For additional commands, e-mail: user-h...@cassandra.apache.org > > > > > > > > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: user-unsubscr...@cassandra.apache.org > For additional commands, e-mail: user-h...@cassandra.apache.org > >
