LVM; Advantages vs. Disadvantages

Vintendo · 2008-06-12 22:59:02

I was just browsing the wiki for some features i would like and i came across LVM. It sounds great!, i have currently three disks in my system. One 640GB, one 750GB and one brand new 1000GB drive and i would like to make them into one large volume. I have heard of Raid 0 but it's too dangerous. Then there is raid 5 but then i need all the same size disks, and i don't have that. Also i lose one disk in storage, but that's not too big of a problem. But with LVM you can use drives of different sizes. I'm just wondering, if one drive fails, do i lose all my data? Can i add and remove drives without reformatting the entire group? I'm planning on putting it on /home. So are there LVM users out there? What do you recommend?

Last edited by Vintendo (2008-06-12 23:42:53)

vogt · 2008-06-13 01:15:12

Lvm does not by default provide any redundancy (I think it has some options for mirroring volumes (raid 1), but those aren't commonly used).

If a disk fails, you loose the data on that disk and by default lvm does not stripe data across disks (but it may be able to), so there will still be some recoverable data (it may take some effort though).

If you have enough unallocated space, you can remove a disk, move the logical volumes while running; its quite flexible. You can combine your storage into one pool, yet still have some control over where it is stored.

Software raid (whatever level), can work across differently sized disks, if the raid is combining similarly sized partitions (on different disks of course), and lvm can take the leftover space too.

One of the drawbacks is that it will take a bit more effort to read the disks in another system, or from another operating system (ie. IFS does not work)

The setup is a bit daunting at first, especially if you put root on lvm/raid, but it is pretty logical, and the documentation is decent.

Vintendo · 2008-06-13 08:31:48

I understand that Lvm doesn't provide redundancy. But how much effort wil it take to recover de data from the other two disk if one fails?

I'm not planning on putting my root on Lvm, yet.

Thank you for the information

Berticus · 2008-06-13 14:09:59

You could prevent this by putting the LVM on top of a RAID 1. There's also this: http://grover.open2space.com/node/17 (At the very bottom before the conclusion). I did't read too much into it.

You may also take preventative action with LVM snapshots, and you can do that every few months or something.

One disadvantage about LVM, is it sort of negates the advantages of having a journal in journal file systems. Not completely though. In my personal experience, I've had a system crash once or twice, and every single time, the journals has pulled through for me.

I believe there are also software available (not open source and not free) that can recover data from LVM if a disk has died on you.

Vintendo · 2008-06-13 15:00:42

Raid 1 is too much of a waste. I have everything backed up right now, but i just wanted to know. The reason why i wanted to install LVM is it makes it a lot easier too manage the hard drives. I think im going to spend the weekend reading a lot... If someone has any experiences, please do tell..

Berticus · 2008-06-13 15:03:34

This is the only thing you need: http://www.tldp.org/HOWTO/LVM-HOWTO/index.html. That's really the only thing I use when I need to add/subtract stuff from my logical volumes. I haven't ran into a problem yet.

Vintendo · 2008-06-14 09:31:03

I have created my LVM volume and i love it. It was way easier then i thought. Now i have a 2.1 TeraByte partition

Arch Linux

#1 2008-06-12 22:59:02

LVM; Advantages vs. Disadvantages

#2 2008-06-13 01:15:12

Re: LVM; Advantages vs. Disadvantages

#3 2008-06-13 08:31:48

Re: LVM; Advantages vs. Disadvantages

#4 2008-06-13 14:09:59

Re: LVM; Advantages vs. Disadvantages

#5 2008-06-13 15:00:42

Re: LVM; Advantages vs. Disadvantages

#6 2008-06-13 15:03:34

Re: LVM; Advantages vs. Disadvantages

#7 2008-06-14 09:31:03

Re: LVM; Advantages vs. Disadvantages

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