[plug] Home Server LVM/RAID stuff

[Marcos Raul Carot Collins]

Hi Trevor!

I have no raid on lvm or lvm on raid, but I have both technologies in use.

Regarding RAID1 via software, you can RAID whatever you want, no need to raid 
the whole disk. Just have 2 partitions of the same size in 2 different HDs 
and make a RAID1 of that partitions.

If I had to choose, I would do LVM and on top of that the RAID1 if just 
RAIDing 1 partiton but would do the RAID1 and on top of that the LVM if 
RAIDing the whole disks.

LVM is so cool. You only understand how cool it is when you run out of space 
and you don't have LVM :P

Also, LVM is quite easy to setup (and some distros offer it at install time, 
such as Debian, which also offers RAID setup at install time).

For LVM just follow http://tldp.org/HOWTO/LVM-HOWTO/commontask.html which has 
the following topics:

11.1. Initializing disks or disk partitions
11.2. Creating a volume group
11.3. Activating a volume group
11.4. Removing a volume group
11.5. Adding physical volumes to a volume group
11.6. Removing physical volumes from a volume group
11.7. Creating a logical volume
11.8. Removing a logical volume
11.9. Extending a logical volume
11.10. Reducing a logical volume
11.11. Migrating data off of a physical volume

All the rest of the how to is mostly theory (is good reading, but you don't 
absolutely need it to implement LVM).

If you need any help, you know I work at about 200m from you :) -unless you 
are ANOTHER Trevor Phillips!-

Cheers!

Marcos R Carot Collins

El Tue, 19 Aug 2008 05:03:35 pm Trevor Phillips escribió:
> I have a home server, and am living in the stone age, it seems - just
> standard physical partitions. Adding disk is easy enough, but then the
> new space is on a new mount point, no redundancy, running out of
> space, yadda yadda...
>
> Recently, a friend raved about how wonderful Windows Home Server was -
> and it did sound quite impressive, what it was capable of. It's
> motivated me to pull my finger out and try and do things better (and
> safer) on my home server. However, my Linux server already does stuff
> Windows Home Server never will - and this is the PLUG list - so I've
> been reading up on similar Linux solutions.
>
> There's basically two key features I'd really really like:
>
> 1) Being able to add more disk, and add that space to existing
> partitions: LVM seems to fit this spot-on.
> 2) Being able to have data redundancy on SOME content, across drives,
> in case of physical failure. Linux Software Raid sort of does this.
>
> Now, really, only about 1/4 of my data I really need redundancy on.
> You know, important stuff like photos, mail, tax documents, etc... All
> the rest is typically regainable (ripped CDs/Video), or I wouldn't
> shed too many tears over losing. So a full RAID1 config is way
> overkill. Yes, disk is cheap, but the Wife won't necessarily buy that
> argument. -_^
>
> Back to Windows Home Server - this does both these tasks in one. You
> can throw in more disk, have it add to volumes as you want, and you
> can also tag content (I believe it's per FOLDER, not even per volume)
> to keep a redundant copy on separate physical disks. It sounds like
> doing all this, and changing the configuration, is a cinch.
>
> So far, the best solution to me sounds like it involves creating 2
> partitions (on separate disk, same size), RAID1ing them, and using
> that for my important data, then using LVM for the rest of the less
> important bulky data. Probably best to even use LVM with the RAID1 as
> well.
>
> I've read 2 ways of treating this LVM/RAID combo though - one was to
> RAID the physical partitions, then create the LVM out of the resultant
> raid partition. The other was to create 2 LVM logical partitions, in
> separate groups, on separate disks, and RAID on top of that.
>
> The former sounds neater, more efficient - but also sounds like it has
> the old problem of being difficult to resize. I guess you could create
> extra partitions later, RAID them separately, then add them to the LVM
> of the first raid, but it seems tricky.
>
> The latter sounds messier, but potentially easier to resize the raided
> content later, since the RAID partitions are on LVM partitions, which
> can be extended more easily.
>
> What experiences have others had with setting up a similar setup? How
> do these two solutions compare for performance & flexibility?
>
> Are there any other neat solutions to do what I want? Ideally I wish
> LVM could handle physical redundancy of a logical partition
> automatically. If Microsoft can do it, why not Linux!
>
> Thanks...