LinuxQuestions.org - [SOLVED] Need advise after adding 4TB disk (FC17, KDE)

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Need advise after adding 4TB disk (FC17, KDE)

Hello,

My FC17+KDE system resides on a pair of 130GB SAS disks
arranged in RAID 0 array /dev/sda and using LVM:

Code:

<root localhost.localdomain>.../root>df

Filesystem                   1K-blocks     Used Available Use% Mounted on

rootfs                       102534472 12835448  84490552  14% /

devtmpfs                       8173528        0   8173528   0% /dev

tmpfs                          8218184      156   8218028   1% /dev/shm

tmpfs                          8218184     1320   8216864   1% /run

/dev/mapper/VolGroup-lv_root 102534472 12835448  84490552  14% /

tmpfs                          8218184        0   8218184   0% /sys/fs/cgroup

tmpfs                          8218184        0   8218184   0% /media

/dev/sda1                      1032088   123232    856428  13% /boot

/dev/mapper/VolGroup-lv_home 135079152 74010164  54207372  58% /home

Recently, after seeing the disk usage growing fast,
I bought a pair of 2TB SAS disks, arranged them too
in another RAID 0 array (well, it had been actually reported
as 3.8TB, the usual disk manufacturers tricks of redefining
measurment units) and started looking for a way to create
an lvm2 volume on the new disk and to mount it on /home/GRAPHICS
(the largest disk space consuming directory).

During the system installation I liked the "disk druid" GUI
program but after some reading I saw it can't be used after the
installation (at least, not in a simple way).

I installed "sys-config-lvm" and "gparted" and looked also
at "lvm" and "cfdisk" and "fdisk".
I would prefate a nice GUI app like "disk druid" but I couldn't
find (or missed) an app to do what I need.
At first I created an "ext4" partition on the /dev/sdb but
then I remembered that I should create physical volume instead
so I deleted the partition.
The "system-config-lvm" didn't see the /dev/sdb disk at all,
in "gparted", looking at the avaliable types of creating a partition
I didn't see any option to create a physical volume (which, AFAIK
is needed to create logical volumes group and then lvm2 volume),
starting "cfdisk" resulted in the following message:

Code:

Warning!! Unsupported GPT (GUID Partition Table) detected. Use GNU Parted.

and then presented what looks like 2TB+1.8TG partitions:

Code:

                                            cfdisk (util-linux 2.21.2)



                                               Disk Drive: /dev/sdb

                                       Size: 3994319585280 bytes, 3994.3 GB

                              Heads: 255   Sectors per Track: 63   Cylinders: 485615



     Name             Flags           Part Type       FS Type                [Label]              Size (MB)

 ----------------------------------------------------------------------------------------------------------------

     sdb1             NC               Primary        GPT                                        2199023.26      *

                                       Pri/Log        Free Space                                 1795296.33      *

I've read about LINUX partition size limits and learned that
I have one more obstacle of which I didn't think earlier.

lookin at /dev/sdb with "gparted" it shows the entire disk "unallocated".

I'm beginning to feel "lost" in what initially looked like a sinple
task of adding a disk to the system.

Can anyone guide me as to what actions should I take to create
ext4 filesystem on LV of 3.8TB on PV resiging on /dev/sdb ?

TIA,

GParted is a really nice GUI but it doesn't support LVM. I know Red Hat / Fedora has a GUI tool specifically for LVM. But I don't know of a GUI that does both LVM and File System stuff. :(

I don't have much experience with software RAID. But assuming /dev/sdb is a RAID block device I would do the following things.
(But first... Note: Making changes to partition tables and filesystems can result in complete loss of data. You are ultimately responsible for your data. IE, have a backup, understand commands, don't copy/paste commands.)

Use fdisk to delete all partitions

LVM:

Code:

pvcreate /dev/sdb

vgextend VolGroup /dev/sdb

lvcreate -l 100%PVS -n lv_graphics VolGroup /dev/sdb

File system and mount:

Code:

mkfs.ext4 /dev/mapper/VolGroup-lv_graphics

mount /dev/mapper/VolGroup-lv_graphics /home/GRAPHICS

Size restrictions shouldn't be an issue here. EXT4 supports up to 16TB and I honestly don't know if there is any limit to LVM.
I would caution you about the RAID 0. Make sure you have backups.

Another thing you can do is just attach both disks and use LVM to combine them into a single volume. That might be easier to manage then a RAID. You could more easily expand or shrink the volume.

Hope that helps some.

Hi jasohl, thanks for the reply.

In fact, after some more reading and searching among the commands
I found that using the "gdisk /dev/sdb" I can create the GPT-type
partition ("LINUX LVM", type code: "8E00") and after that
I could use the "system-config-lvm" to create the physical
volume, logical group and logical volume. Currently, it's
mounted on a slightly differently named directory than my
final intention:

Code:

<localhost.localdomain>.../user>df

Filesystem                                 1K-blocks     Used  Available Use% Mounted on

rootfs                                     102534472 12850732   84475268  14% /

devtmpfs                                     8173528        0    8173528   0% /dev

tmpfs                                        8218184      152    8218032   1% /dev/shm

tmpfs                                        8218184     1256    8216928   1% /run

/dev/mapper/VolGroup-lv_root               102534472 12850732   84475268  14% /

tmpfs                                        8218184        0    8218184   0% /sys/fs/cgroup

tmpfs                                        8218184        0    8218184   0% /media

/dev/sda1                                    1032088   123232     856428  13% /boot

/dev/mapper/VolGroup-lv_home               135079152 73994472   54223064  58% /home

/dev/mapper/VolGroup_graphics-lv_graphics 3839491472 23288632 3621167912   1% /home/user/GRAPHICS_lv

After I'll compare the contents of the old GRAPHICS
and the new GRAPHICS_lv directories, I'll need to
boot LINUX into command line mode (without the desktop coming up),
to rename "GRAPHICS" to "GRAPHICS_old", to rename "GRAPHICS_lv"
to "GRAPHICS", to edit appropriately the /etc/fstab, to reboot
and hopefully the GUI (with various links from GRAPHICS to the desktop)
won't notice any change.

Now I need to find out how to pause the boot process and
force the command line boot...

TIA,

Solved!

It took some time to figure out where to add the "3" on the grub2 menu (most searches showed a single line command,
not a multi-line entry) but finally I could boot without desktop starting, to rename "GRAPHICS" to "GRAPHICS_old",
to attempt renaming "GRAPHICS_lv" to "GRAPHICS, to encounter an error "device busy" (or something like
thhis), to attempt unmount, to get the same error, to rename back, to reboot normally, to comment the line in /etc/fstab
which mounts the new disk, to reboot into command line, this time to successfully rename everything
as I want, to replace /etc/fstab with the one with mount command to "GRAPHICS" instead of "GRAPHICS_lv"
and after reboot - everything is as I want it: new 3.6 TB disk (hardware RAID 0) is mounted on "GRAPHICS"
directory.

Thanks for all the help,
kaza.