Resizing an LVM partition

oogs · 10-23-2008, 09:49 PM

Hi,

I'm new here, but not to forums in general. Before someone replies with "search for the answer", I'll say that I did and came up with this:

(can't post link as this is my first post. nice anti-spam trick!)

I just want to make sure that the solution to my problem right before I go do it.

First off, here's the problem:
I have a 5-drive RAID 5 setup, and I want to add a 6th to it, and expand my / partition (sda2).

The setup:

Fedora Core 3 on a Dell PowerEdge 2850. There are 5 drives, each 143GB SCSI, in RAID 5. I know that the PERC 4 raid card can handle resizing the RAID, so I'm looking to add a 6th. I have an Ubuntu Live CD that has:
- the drivers for my raid
- gparted, which sadly doesn't do the trick
- lvm tools, which does do the trick.

fdisk produces this output after I add the drive:

Code:

Command (m for help): p

Disk /dev/sda: 733.4 GB, 733478912000 bytes
255 heads, 63 sectors/track, 89173 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14       71338   572918062+  8e  Linux LVM

Command (m for help): q

So the next step is with that guide, right?

# lvm vgchange -a y
# e2fsck -f /dev/VolGroup00/LogVol00
# resize2fs -f /dev/VolGroup00/LogVol00 (size??)
# lvresize -L(size??) /dev/VolGroup00/LogVol00

sda1 is a mere 100M, so should (size??) be the full 733G? Also, how long will this take? Again, I'm really just seeking confirmation before I do something I can't fix.

Thanks for any feedback!

oogs · 10-24-2008, 02:12 PM

I guess I should mention, I'm trying to do this w/o destroying the data on the partition.

GazL · 10-24-2008, 03:03 PM

Please don't take this the wrong way but I don't think you fully understand the concepts of the things your dealing with here. What you've listed above won't work for you. Please be careful.

From what I can figure out from what you've posted:

You have a 5 disk hardware raid array on a PERC 4 controller which your system sees as a single disk device /dev/sda

On that array you have sda1 (which I'm guessing by its size is mounted as /boot?)
and sda2(type 8e) which is your LVM Physical Volume (PV) and holds your volume group and all its Logical Volumes.

Now, if you add a 6th disk to the array and instruct the controller to rebuild/extend the array, my understanding of what will happen is that the size of /dev/sda will increase, but the size of sda2 will not and therefore you won't be able to use the extra space in LVM.

I'm not aware of anyway to increase the size of a PV (your sda2 partition), someone please correct me if there is.

So the only non-disruptive way I can see would be to:

Non-disruptively extend your hardware Raid array however you do it.
(I don't have any knowledge of the PERC controllers so I can't help you with that)
Create a new type 8e LVM partition as sda3 to use the newly created free space on /dev/sda.
Create a new lvm PV on sda3 with 'pvcreate'.
Add the new pv sda3 to the Volume Group with 'vgextend'
And then extend the Logical Volumes you want to extend as you describe above.

It's not pretty, but it should work.

I hope that gives you somewhere to start from, but changing storage subsystems is not something to attempt lightly. I urge you to look into this fully before trying anything.

Gaz.

oogs · 10-24-2008, 03:30 PM

Actually, that's exactly what I was looking for - someone telling me that I'm either right or wrong. And I'm not taking this lightly either, that's why I'm asking for help. So, Thank you!

Edit: I'm working on the concepts too.

As for your assumptions:

- Yes, that's the raid setup.
- sda1 is /boot
- adding the 6th drive *did* increase sda.

Quote:

* Non-disruptively extend your hardware Raid array however you do it.
(I don't have any knowledge of the PERC controllers so I can't help you with that)
* Create a new type 8e LVM partition as sda3 to use the newly created free space on /dev/sda.
* Create a new lvm PV on sda3 with 'pvcreate'.
* Add the new pv sda3 to the Volume Group with 'vgextend'
* And then extend the Logical Volumes you want to extend as you describe above.

I've already done step 1 using dellmgr. Steps 2-5 seem pretty straightforward (fdisk & mkfs, then lvm stuff). I don't care if it's an ugly solution as long as it works.

GazL · 10-24-2008, 07:47 PM

Quote:

Originally Posted by oogs

I've already done step 1 using dellmgr. Steps 2-5 seem pretty straightforward (fdisk & mkfs, then lvm stuff). I don't care if it's an ugly solution as long as it works.

I'm glad your getting closer Oogs.

If all you're doing is adding space to existing filesystems you shouldn't need to do a mkfs. When you do the pvcreate and vgextend commands that will add the new freespace to lvm ready for use. From that point on all you have to do is find the right logical volume for the filesystem you want to increase. The pvs or vgdisplay commands will show you if the new space is available for use.

BTW, I've just noticed that you've got the order slightly wrong on those commands you listed to actually extend the LVs. It should be

lvextend
e2fsck
resize2fs

As for the resize2fs, you shouldn't need to specify a size. If you leave the size blank it should resize to whatever space you've allocated to it with the lvextend.

For specifying the size on the lvextend you've got a couple of options, specify absolute size or a relative amount to add to the existing LV. (It's all on the man page).

Anyway, Good luck with it all. Wish I had a 700+ GB raid array to play with. I love playing with storage/LVM. I'm sad that way.

oogs · 10-24-2008, 08:52 PM

Hehe, it wasn't as much play as "get it done before we run out of room!" I did manage to get it done though, and I realized that the commands were out of order b/c they complained that something (the filesystem, size, etc) wasn't right. So now I have the 700GB not-so-pretty-yet-functional partition!