Thread: replication between US <-> EU

Hi,

I would like to get some ideas about subject. I do not have any
preferred solution (hot-standby, Slony or pgpoll) so anything which
can deliver/satisfy the following will good:

- one side completely down: Client should use switch to other side
transparently (Failover / High Availability)

- database writes: transparent for application ie. connection
pooler/... should redirect writes to master (it would be nice to have
writes on both sides and everything in sync) and use local database
for reads (database holds metadata/configuration; just few writes)

- replication lag: Clients shouldn't use "stalled data". Switch to
master or stop and wait are preferred actions.

- automatic failover w/o DBA intervention (or minimal intervention)

The other things to consider are:

- average latency could be up to 400ms. There is no problem to buy
connectivity from different provider if we can use simpler/more robust
setup. But I don't know which provider can deliver low latency link
suitable for this purpose.

- one second lag between master and slave would be tolerable but if we
can go lower that would be nice (low latency link, configuration, ...)
but we need robustness

- kernel or tcp/ip tweaks? We use CentOS 5.7

- database is small; around 1.5GB. It doubles in size every 6..9 months.

- NetScaler like appliance could be used

Thanks!

--
Ondrej Ivanic
(ondrej.ivanic@gmail.com)

On 03/06/12 3:31 PM, Ondrej Ivanič wrote:
> - one side completely down: Client should use switch to other side
> transparently (Failover / High Availability)

what happens if the link between the sites is down and both sides decide
they are master?  then how do you put the pieces back together ?



--
john r pierce                            N 37, W 122
santa cruz ca                         mid-left coast

Hi,

On 7 March 2012 10:36, John R Pierce <pierce@hogranch.com> wrote:
> On 03/06/12 3:31 PM, Ondrej Ivanič wrote:
>>
>> - one side completely down: Client should use switch to other side
>> transparently (Failover / High Availability)
>
>
> what happens if the link between the sites is down and both sides decide
> they are master?  then how do you put the pieces back together ?

Good catch! From application point of it is quite easy to sync data
between sites. Let's assume that writes should be disabled in this
scenario.

--
Ondrej Ivanic
(ondrej.ivanic@gmail.com)