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I'm setting up a CentOS dedicated server and I would like to use LVM (it's the right thing to do, isn't it?)

The thing is, I'm not sure if I have an option to enable LVM at the time of installation. Can I enable it later? Is it advisable to enable it while installing from scratch, if possible?

My server has 2 hard drives, which are not currently used as RAID, but I would like to use them as RAID 1. But I guess that's another question.

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You can enable it later, but enabling it won't magically convert your root partition into an LVM volume. If you install on LVM, you'll have LVM controlling the OS partitions as well as anything you add later; if you don't, it'll only be things you add later that are LVM'ed.

The same is generally true of RAID - if you want the OS to live on RAID, it's a lot easier to set up at install time (cute as the linked question thing is, they're not really two different questions; or at least, they could very easily be handled in the same posting).

Having the OS on RAID-1 is a no-brainer, for me; I don't know why anyone wouldn't do it, comparing the cost of hard drives with the cost of admins and downtime when a drive fails. Note that RAID-1, although excellent, is not a substitute for backups.

As for whether having the OS on LVM is the right thing to do, that's more of a judgement call / matter of opinion. My personal feeling is that if the machine is going to be stable after installation - it's a fire-and-forget machine, where you'll never want to resize a disc or re-partition any of the volumes - then there's little point in the added complexity of LVM. If, however, this machine might have a more interesting life, then LVM can be of very material assistance when you're resizing / moving / adding drives later on.

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And to add to this: I believe the option to enable it in CentOS is when it asks if you want to change the layout of the disk. –  Safado Mar 24 at 14:47
    
You can also use LVM's volume mirroring capabilities to get the equivalent of RAID-1, rather than having half of each disk a PV for LVM and the other half a device for RAID. –  John Mar 24 at 14:47
    
@John, can you tell where should I look for the mirroring capabilities of LVM? Also, could you please explain the alternate scenario you are describing? –  Nickolai Leschov Mar 24 at 14:52
    
man lvcreate, man lvextend –  John Mar 24 at 14:57

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