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
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