[Linux-cluster] Cluster among geographically separated nodes ?

[Giuseppe Fuggiano]

2009/6/18 Gordan Bobic <gordan at bobich.net>:
> On Thu, 18 Jun 2009 17:11:42 +0530, Brahadambal Srinivasan
> <brahadambal at gmail.com> wrote:
>> Hi,
>>
>> I am trying to figure out if it is possible to create an RHCS cluster
> among
>> nodes that are in remote locations? If yes, then how are the following
>> handled? :
>>
>> 1. Storage - how is the shared storage acheived?
>
> Same as it is achieved locally. It is up to your SAN to handle this in a
> real-time, consistent way. You may want to look into DRBD
> (http://www.drbd.org) for the block device level replication. Be aware,
> however, that performance on the disk access front will be terrible,
> because the latency will end up being limited by your ping time on the WAN.
> So instead of it having 0.1ms added via a local gigabit interconnect, it'll
> have 50-100ms added to it. Most applications will not produce usable
> performance with this kind of disk I/O speed.

I am wondering if that will affect both read and write requests or
only write/verify ones (which DRBD have to replicate using the
network).

-- 
Giuseppe