On 03/20/2014 11:27 AM, Mark Haney wrote:
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On 03/20/14 12:51, CS_DBA wrote:
So we're looking at database failover, application connections to
the db are via I.P.'s (or aliases) we can of course use ifconfig
and create/destroy aliases and thus "move" the IP aliases at
failover time, however I would like to leverage a tool so the IP
alias move can be both seamless and executable via command(s) on a
single server.
With ifconfig aliases we need to do the following in the failover
script: - execute the ifdown on the old / failed master server
(probably via commands over ssh) - validate that the ip alias came
down - execute the ifup of the alias on the slave (going to be the
new master shortly) - verify that it came up - then finish the db
failover
I've been in a similar situation before, and here's what I did.
Instead of failing over from one to another, use round-robin DNS and
replicate the DB between servers. My original setup was with 2 DB
servers with a backend GigE fiber connection with as close to
real-time replication as I could make it. This kept the data
consistent and let me take one down if I needed to, or if one failed
round robin would send connections to the live DB.
I ended up scaling it up from 2 Db servers to 4, 2 live servers, 2
'backup' servers that I could make live if my primaries were hit
really hard, or would be backups if one of my primaries died.
RR DNS and DB replication is your friend here. Mucking with IP
aliases might sound good initially, and it may be fine for a while,
but I would consider long-term improvements. My situation was kind of
special due to the demands of MilSpec with the SGI Altix HPCCs and DB
servers I managed, but this setup will work in almost every situation.
I'll be glad to offer any assistance off-list if you like.
we're running PostgreSQL and Streaming replication which means that we
can only write to the master.
Were both of your db's read/write nodes? What db platform?
- --
Mark Haney
Network/Systems Administrator
Practichem
W: (919) 714-8428
Fedora release 20 (Heisenbug) 3.13.6-200.fc20.x86_64
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