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Re: [Linux-cluster] help on configuring a shared gfs volume in a load balanced http cluster



So, shd machines are actually SANs. You will need to use something like DRBD if you want shd machines mirrored and ATAoE or iSCSI to export the volumes for the rs machines to mount.

Then create a shared GFS on the ATAoE/iSCSI device.
You may, however, find that for web servers (lots of small files, frequent access to same files from all nodes) NFS/NAS gives you better performance, with shds configured mirrored for fail-over by not load balanced (warm standby).

If you need very high performance / low latencies from storage, you may want to look into something like seznamfs for replicating content from a single master server to multiple slaves (DAS).

Gordan

On Thu, 24 Jul 2008, Alex wrote:

Hello cluster experts,

I'm new here and new to cluster world too... I need some help, in order to
setup a cluster in our organization.

Shortly, our schema is:

2 routers for HA and load balancing
- ar (active router)
- br (backup router)

3 http servers located internaly acting as real web servers (rs1, rs2, rs3)
behind
ar and br routers.
rs1=192.168.113.3/24
rs2=192.168.113.4/24
rs3=192.168.113.5/24

2 shared data servers (shd1, shd2)
shd1=192.168.113.6/24
shd1=192.168.113.7/24

1 server for cluster management (rhclm)
rhclm=192.168.113.8/24

I've configured ar and br routers for high availability and load banacing and
everything is ok. Active router (ar) are forwarding http requests to VIP
(floating) external ip address to internaly ip addresses of rs1, rs2, rs3
webservers.

Now, i don't know how to:
- configure and group some hard disks on our shd1 and sdh2 servers to
form a shared volume for our rs1, rs2, rs3 real servers (i suppose that the
correct topic should be shared volume using GFS...)
- make usable this volume and act as DOCUMENT ROOT on our rs1, rs2 and rs3
webservers.

All our servers are running centos 5.2 and has all updates installed.

On rhclm (192.168.113.8) i installed cana and created a cluster with 2 nodes:
shd1 and shd2.

Cana, generated the following cluster.conf on shd1 and shd2 servers:

[root shd1 ~]# cat /etc/cluster/cluster.conf
<?xml version="1.0"?>
<cluster alias="wwwdata" config_version="2" name="wwwdata">
       <fence_daemon clean_start="0" post_fail_delay="0"
post_join_delay="3"/>
       <clusternodes>
               <clusternode name="192.168.113.7" nodeid="1" votes="1">
                       <fence/>
               </clusternode>
               <clusternode name="192.168.113.6" nodeid="2" votes="1">
                       <fence/>
               </clusternode>
       </clusternodes>
       <cman expected_votes="1" two_node="1"/>
       <fencedevices/>
       <rm>
               <failoverdomains/>
               <resources/>
       </rm>
       <totem consensus="4800" join="60" token="10000"
token_retransmits_before_loss_const="20"/>
</cluster>

Now, on shd1 i am using hda for centos OS and hdb (1,2) i want to make it
available to be used on shared volume:

[root shd1 ~]# cat /proc/partitions
major minor  #blocks  name
  3    64   39082680 hdb
  3    65   19541056 hdb1
  3    66   19541592 hdb2
[root shd1 ~]#

on shd2 i have hda for centos and hdc (1,2) i want it available to be used on
shared volume:
[root shd2 ~]# cat /proc/partitions
major minor  #blocks  name
 22     0   78150744 hdc
 22     1   39075088 hdc1
 22     2   39075624 hdc2
[root shd2 ~]#

Using cana, i couldn't find a way to create a volume, grouping hdb1 (from
shd1) together with hdc1 (from sdh2) in one volume. I want to do this for 2
reasons:
- i want that volume to be mounted as document root on rs1, rs2, rs3 real
webservers
- i want that volume to be easy to extend adding new hdd on the fly of other
computers to this volume (new hdd slices of other new computers).

Can anybody tell me how can i do it?

I don't know that for this design if correct to have:
- all 5 servers (rs1, rs2, rs3, shd1, shd2) to be configured as nodes in
the same cluster
or
- rs1, rs2, rs3 to be part of one cluster and shd1 and shd2 to form another
cluster

I read section: A.2. Configuring Shared Storage in this document
http://www.centos.org/docs/5/html/Cluster_Administration/ap-httpd-service-CA.html
but is not what i want.

Can anybody help me. A link pointing me to the correct direction or a howto
will be appreciated.

Regards,
Alx

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