Hi all,
This is my first post here, so I hope you'll be gentle! :o)
I am currently setting up a scalable load-balancing web-cluster however
I can't get my head around a few things. I'll explain what the desired
result is, then I'll explain how I plan to set it up, then I'll let
people tell me that I'm wrong! :oP
I've search the archives and google, however as I'm not entirely sure
what the name is for what I'm trying to achieve, I've not had much luck
finding a solution.
I've set heartbeat up in the past on a simple two-node cluster with
great success, however this time, it's a bit more complicated...
1) What I want to achieve:
- There are two director servers and n web nodes in the arrangement
- The director servers provide the (virtual) external IP address for DNS
records etc so that the content held on the web nodes can be
load-balanced
- The director servers also provide LDAP authentication for FTP users
on each of the web nodes ensuring that even if one director and the
primary web node is down, ftp access and permissions are still
maintained.
- The director servers also hold a replicated MySQL database for
apache2 logging using mod_log_mysql and an NFS share that holds a
nightly log-dump so that awstats can be run on each web node
The system should be able to cope with the following:
a) A Director Outage
b) A Web Node Outage
c) A Network Outage
2) What I currently have (excuse the poor ascii art!):
'----------' heartbeat '----------'
|Director 1|------------|Director 2|
'----------' '----------'
| |
'--------' '--------'
|Switch 1|______ |Switch 2|
'--------' ____X______/'--------'
| / \ |
'---------' \ '---------'
|Webnode 1| \____|Webnode 2|
'---------' '---------'
I hope that the following will give me complete redundancy on a
network, director and node level however the issue I am encountering is
with the way in which the IP Addresses are assigned to the interfaces.
Currently, the Directors have Three NICs in them - WAN (+virtual IP),
LAN (+virtual IP) & Heartbeat
The web-nodes also have three NICs - WAN, LAN1, LAN2
I am trying to complete this task by applying Occam's Razor[0], although
I'm not sure that you can in this kind of situation.
My planned IP Addressing is as follows:
Director 1:
WAN - what ever is assigned by the Data Centre (inc. virtual IP)
LAN - 10.27.1.201 (x corresponds to the director number)
LAN (Virtual) - 10.27.1.254
Director 2:
WAN - what ever is assigned by the Data Centre (inc. virtual IP)
LAN - 10.27.1.202 (x corresponds to the director number)
LAN (Virtual) - 10.27.1.254
WebNode 1:
WAN - what ever is assigned by the Data Centre
LAN1 - 10.27.1.101
LAN2 - 10.27.1.102
WebNode 2:
WAN - what ever is assigned by the Data Centre
LAN1 - 10.27.1.103
LAN2 - 10.27.1.104
The issue that I am encountering is that when a webnode has two
interfaces that are on the same subnet, I can ssh to one, but if I try
and ssh to the other it fails.
I think that I may end up requiring a subnet for each network that is
connected to a director (i.e. 10.27.1.x for director1 and 10.27.2.x for
director2) and a third "virtual" subnet (on eth0:0 for example) for the
HA stuff. This seems unnecessarily complex to me, and I'm sure there's
a better way of doing it!
3) Here it is folks - your excuse to tell me why I'm wrong and where I
need to look/read/research/test in order to fix this issue.
Thanks in advance for any help,
Kind regards,
Matt
[0] To paraphrase - "everything in it's simplest form, but no simpler"
--
Matthew Macdonald-Wallace
[EMAIL PROTECTED]
http://www.truthisfreedom.org.uk
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