14th Sep 2006

Enable LVM on software-RAID during a Suse installation

If you have tried setting up LVM on top of a LVM-enabled software-RAID partition during a standard Suse installation you may have hit a brick wall where the installer tells you that there are no available LVM partitions. This is a bug in the installer, it looks as if the LVM setup tool only checks physical partitions for LVM labels and ignores software-RAID partitions that have LVM labels.

Steve Wray has pointed out that you can get this functionality to work by creating a small physical partition and giving it an LVM label. The LVM setup tool will see this partition and allow the configuration to continue quite happily with the software-RAID partitions available for use. I have not tested this but I think it is worth giving a spin as the data integrity of RAID-1 coupled with the flexibility of LVM is a compelling combination (though performance maybe an issue).

5th Sep 2005

Adventures in LVM

In recent times I have been using Logical Volume Management (LVM) on Linux as a very flexible way of operating a flexible file system. LVM is a very powerful way of dynamically adding and removing disk from a Linux server (or desktop). Rather than mounting individual devices in different parts of the file system LVM lets you place all your physical disk drives together into virtual pools. Inside these pools you can dynamically divide the space up however your like and format each partition in any of the available Linux file formats.

It is a great way to work with disk resources and is very similar to Novell's Network Storage Services (NSS) volumes (minus the very useful 'salvage' tool). To get around the lack of a salvage tool you can create regular snapshots of your data. These snapshots are like CVS branches in that rather than creating a separate copy of the data a snapshot tracks what has changed on disk from a particular time.
For example to create a snapshot of your 'data' volume you perform the following command (Note: you must have the dm-snapshot module loaded into the kernel):

lvcreate -L10G -s -n salvage /dev/system/data