[CentOS] Design question about VG / LV in a clustered environement

Wed Dec 7 03:56:03 UTC 2011
Nicolas Ross <rossnick-lists at cybercat.ca>

Hi !

Since the last couple of months, we had a few problems with the maner we 
designed our clustered filesystem and we are planing to do a re-design 
of the filesystems and how they are used.

Our cluster is composed of 8 nodes, connected via fibre channel, to a 
raid enclosure where we have 6 pair of 1-tb drives in mirror, so 6 1tb 
physical volumes.

First of all, our services that are run from the cluster are running 
inside of directories. For exemple, a webserver for a given application 
is run from /CyberCat/WebServer/(...) That directory contains all 
executable (apache, php for exemple) and the related data, except for 
the databases. /CyberCat being a single GFS partition containing several 
other services.

This filesystem and another one like this containing services for some 
other clients occupy a single VG composed of 2 PV (total 2tb). The 
remaining (4) other PV are used in one 1tb VG each, and those VG 
contains only one LV that is used for databases servers.

For availibility reasons, we are planing of spliting the /CyberCat (and 
the other one like it) FS into several smaller filesystems, one for each 

The reason being that in the event that we need to make a filesystem 
check, or any other unplaned reason, on any filesystem it won't affect 
other services.

So, now comes the question I have :

1. First of all, is this a bad idea ?

2. Is there any disadvantages of doing a single volume group composed of 
many physical volumes, enabling us to move the extents of a logical 
volume from one physical volume to another one, so that load is more 
balanced in the event we need it.

Thanks for the input.