On 09/08/2015 04:44 PM, Jonathan Proulx wrote:
Hi All,
I'm pretty close to opening a second region in my cloud at a second
physical location.
The plan so far had been to only share keystone between the regions
(nova, glance, cinder etc would be distinct) and implement this by
using MariaDB with galera replication between sites with each site
having it's own gmcast_segment to minimize the long distance catter
plus a 3rd site with a galera arbitrator for the obvious reason.
I would also strongly consider adding the Glance registry database to
the same cross-WAN Galera cluster. At AT&T, we had such a setup for
Keystone and Glance registry databases at 10+ deployment zones across 6+
datacenters across the nation. Besides adjusting the latency timeout for
the Galera settings, we made no other modifications to our
internal-to-an-availability-zone Nova database Galera cluster settings.
The Keystone and Glance registry databases have a virtually identical
read and write data access pattern: small record/row size, small number
of INSERTs, virtually no UPDATE and DELETE calls, and heavy SELECT
operations on a small data set. This data access pattern is an ideal fit
for a WAN-replicated Galera cluster.
Today I was warned against using this in a multi writer setup. I'd planned
on one writer per physical location.
I don't know who warned you about this, but it's not an issue in the
real world. We ran in full multi-writer mode, with each deployment zone
writing to and reading from its nearest Galera cluster nodes. No issues.
Best,
-jay
I had been under the impression this was the 'done thing' for
geographically sepperate regions, was I wrong? Should I replicate just
for DR and always pick a single possible remote write site?
site to site link is 2x10G (different physical paths), short link is
2.2ms average latency (2.1ms low, 2.5ms high over 250 packets) long
link shouldn't be much longer but isn't yet complete to test.
-Jon
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