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LVM with EXT3 fs

Good news everyone! In next how-to is explained good technique, how to resize you partition when you are not sure about their size. LVM is the best tool for managining you partition resizeable. In my example I have set up not system partition, but data storege on CentOs box, because there is allways problem that disk can get broken a need for buing new one. I have set up two EXT3 fs partition on this disk using LVM. They are /data and /var/www. Size of this fs can be changed, so you do not need to worry, when you do not estimate size for fs. Disk is 250GB and at the end of this how-to is shown, how to resize the fs. The disk is already prepared using fdisk utility and it is devided to one primary partition with Linux LVM type, which containes whole capacity. This partiotion is used for LVM.

1. Creating physical extend on disk and volume group used in next step for logical volume:

[root@virus roleta]# fdisk -l

Disk /dev/hdb: 20.0 GB, 20020396032 bytes
255 heads, 63 sectors/track, 2434 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdb1   *           1          65      522081   83  Linux
/dev/hdb2              66         830     6144862+  83  Linux
/dev/hdb3             831        1595     6144862+  83  Linux
/dev/hdb4            1596        2434     6739267+   5  Extended
/dev/hdb5            1596        1977     3068383+  83  Linux
/dev/hdb6            1978        2232     2048256   83  Linux
/dev/hdb7            2233        2297      522081   82  Linux swap / Solaris
/dev/hdb8            2298        2434     1100421   83  Linux

Disk /dev/hdd: 251.0 GB, 251000193024 bytes
255 heads, 63 sectors/track, 30515 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdd1               1       30515   245111737   8e  Linux LVM
[root@virus roleta]# pvcreate /dev/hdd1
  Physical volume "/dev/hdd1" successfully created
[root@virus roleta]# vgcreate storage /dev/hdd1
  Volume group "storage" successfully created
[root@virus roleta]# vgdisplay
  --- Volume group ---
  VG Name               storage
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  1
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               233.75 GB
  PE Size               4.00 MB
  Total PE              59841
  Alloc PE / Size       0 / 0
  Free  PE / Size       59841 / 233.75 GB
  VG UUID               UUTi0n-8XQh-at8Y-AmUJ-G6lo-yLdd-LM2UsQ

[root@virus roleta]#

On disk was volume group created. It is physical abstraction of the disk. On this volume group can be created logical volume, whitch is abstraction for creating of new fs.

2. Creating of logical volume as a base for new filesystem:

[root@virus roleta]# lvcreate -L40G -nweb storage
  Logical volume "web" created
[root@virus roleta]# lvcreate -L185G -ndata storage
  Logical volume "data" created
[root@virus www]# lvdisplay
  --- Logical volume ---
  LV Name                /dev/storage/web
  VG Name                storage
  LV UUID                Tjr8Wq-UDxO-YOhG-KLT6-27U0-Md9B-XpdqFZ
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                40.00 GB
  Current LE             10240
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0
 --- Logical volume ---
  LV Name                /dev/storage/data
  VG Name                storage
  LV UUID                3H90hO-BEi3-ADXH-ARF8-MicF-fzk7-D0O4wz
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                185.00 GB
  Current LE             47360
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1

[root@virus www]#

On available logical volume can be created filesystems.

3. Creating of fs on logical volume:

  
[root@virus roleta]# mke2fs -j /dev/storage/web
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
5242880 inodes, 10485760 blocks
524288 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
320 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
        4096000, 7962624

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 29 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@virus roleta]# mke2fs -j /dev/storage/data 
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
24248320 inodes, 48496640 blocks
2424832 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=0
1480 block groups
32768 blocks per group, 32768 fragments per group
16384 inodes per group
Superblock backups stored on blocks: 
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
        4096000, 7962624, 11239424, 20480000, 23887872

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 26 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@virus roleta]#

Mounting created fs. After this step new fs can be used. Enjoy.

4. Mounting fs using /etc/fstab:

[root@virus roleta]# cat /etc/fstab 
LABEL=/1                /                       ext3    defaults        1 1
LABEL=/tmp              /tmp                    ext3    defaults        1 2
LABEL=/var              /var                    ext3    defaults        1 2
LABEL=/home             /home                   ext3    defaults        1 2
/dev/hdb2                /backup                        ext3    defaults        1 2
/dev/storage/web     /var/www           ext3    defaults        1 2
/dev/storage/data    /data            ext3    defaults        1 2
LABEL=/boot             /boot                   ext3    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-hdb7         swap                    swap    defaults        0 0
[root@virus roleta]# mount -a
[root@virus roleta]#

Resizing EXT3 fs on LVM

Bad news everyone! CentOs is not supported reiserfs or xfs by default, so I have to use EXT3 fs. It is because I am lazy to modify kernel for abbility to use these fs's. No, ofcourse not, real excuse is that i do not have physical access to this machine and I really worry that something get wrong while upgrading kernel (It won't happend while using Ubuntu!!!!. It has this support by default and upgrade of kernel is without any trouble!).

It is not so bad news at all. The only one difference when using EXT3 fs ist that you have to umount it first. I have read some article that ext3 can be extend even on-line, but I am paranoid that I can possible lost some data. For extending fs please always be sure that you have enought "Free PE" using vgdisplay command. While shring fs be sure that you are able to shrink it to required size.

Shrinking ext3 fs on LVM to 32GB size:

[root@virus roleta]# df /var/www
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/storage-web
                      36124288    180248  34109032   1% /var/www
[root@virus roleta]# umount /var/www
[root@virus roleta]# e2fsck -f /dev/storage/web
e2fsck 1.39 (29-May-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/storage/web: 12/4587520 files (8.3% non-contiguous), 189030/9175040 blocks
[root@virus roleta]# resize2fs /dev/storage/web 32G
resize2fs 1.39 (29-May-2006)
Resizing the filesystem on /dev/storage/web to 8388608 (4k) blocks.
The filesystem on /dev/storage/web is now 8388608 blocks long.

[root@virus roleta]# lvreduce -L 32G /dev/storage/web
  WARNING: Reducing active logical volume to 32.00 GB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce web? [y/n]: y
  Reducing logical volume web to 32.00 GB
  Logical volume web successfully resized
[root@virus roleta]# mount -a
[root@virus roleta]# df /var/www
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/storage-web
                      33027952    180296  31169936   1% /var/www
[root@virus roleta]#

Extend of ext3 fs on LVM to 198GB size:

[root@virus roleta]# df -h /data
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/storage-data
                      192G  253M  182G   1% /data
[root@virus roleta]# umount /data
[root@virus roleta]# e2fsck -f /dev/storage/data
e2fsck 1.39 (29-May-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/storage/data: 30/25559040 files (3.3% non-contiguous), 866668/51118080 blocks
[root@virus roleta]# lvextend -L 198G /dev/storage/data
  Extending logical volume data to 198.00 GB
  Logical volume data successfully resized
[root@virus roleta]# resize2fs /dev/storage/data
resize2fs 1.39 (29-May-2006)
Resizing the filesystem on /dev/storage/data to 51904512 (4k) blocks.
The filesystem on /dev/storage/data is now 51904512 blocks long.

[root@virus roleta]# mount -a
[root@virus roleta]# df -h /data
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/storage-data
                      195G  253M  185G   1% /data
[root@virus roleta]#