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Martin Hope
gdelfino
Asked: 2016-10-12 14:13:08 +0800 CST
  • 1

I am working on a proposal for a system with seven CouchDB servers (A,B,C,D,E,F,G) in different countries. The idea is to configure multi-master replication so that all data can be kept in sync.

I could configure bi-directional replication from each server to each other server

Mathematica graphics

but I suspect that this may result in too many connections that could reduce performance by increasing the used bandwidth (is this the case?).

So my next idea is to configure them like a ring:

Mathematica graphics

Now we have much fewer connections and still have redundancy as each node is connected to two servers. The problem for my particular situation is that we don't want to have all databases in all the nodes. We would like to have two nodes (A & B) with all the databases and the rest with different subsets of it. For this reason I am thinking about doing this:

Mathematica graphics

As I am not a network topology expert, I would like to ask:

  • Is it truly not a good idea to replicate all nodes against all nodes?
  • Is this a reasonable topology (the last shown)?
  • Where could I learn more about this?

Just for completeness, the figures were generated with the following Mathematica commands:

Graph[Rule @@@ Permutations[CharacterRange["A", "G"], {2}],  VertexLabels -> "Name"]
Graph[Rule @@@ (Partition[CharacterRange["A", "G"], 2, 1, {-1}] /. {a_, b_} :> Sequence[{a, b}, {b, a}]), VertexLabels -> "Name"]
Graph[Flatten[Outer[{#1 -> #2, #2 -> #1} &, {"A", "B"}, CharacterRange["C", "G"]]~Join~{"A" -> "B", "B" -> "A"}], VertexLabels -> "Name"]
replication topology couchdb network-topology
Martin Hope
gdelfino
Asked: 2012-02-15 07:17:23 +0800 CST
  • 2

I have installed MariaDB 5.3.3 on a Centos 6 server. In order to do that, I had to issue this command before installing the MariaDB-server rpm:

rpm -e --nodeps mysql-libs

And now mariadb and all the other software in the server is working fine.

Today I tried to upgrade the packages in my server the packages were successfully upgraded with the only exception of postfix which I can't install because of this error:

Running rpm_check_debug
ERROR with rpm_check_debug vs depsolve:
mysql-libs is needed by postfix-2:2.6.6-2.2.el6_1.x86_64
** Found 1 pre-existing rpmdb problem(s), 'yum check' output follows:
2:postfix-2.6.6-2.1.el6_0.x86_64 has missing requires of mysql-libs
Your transaction was saved, rerun it with: yum load-transaction /tmp/yum_save_tx-2012-02-13-09-487yg1lQ.yumtx
.. install failed!

Could anyone help me overcome this problem? I am pretty sure that the software in the mysql-libs package is already installed by mariadb packages but this information ins not in the rpm system.

Additional info:

centos postfix rpm mariadb centos6
Martin Hope
gdelfino
Asked: 2010-07-21 08:27:41 +0800 CST
  • 1

I have a problem with gnu screen.

Computer 1:

open terminal
$ printenv TERM
xterm-color
$ screen
$ printenv TERM
screen

Computer 2:

open terminal
$ printenv TERM
xterm-color
$ screen
$ printenv TERM
xterm-color

Both computers are running Mac OS X 10.6.4, screen version 4.00.03, and similar configuration.

According to screen its man page:

In each window's environment screen opens, the $TERM variable is set to "screen" by default. But when no description for "screen" is installed in the local termcap or terminfo data base, you set $TERM to - say - "vt100".

In both computers I have the terminfo files for "screen" at /opt/local/share/terminfo/73

Even when I do screen -T screen I still get the $TERM variable set as xterm-color

Any ideas?

gnu-screen terminfo