Linux Practicum: Adding a Second Storage Drive on CentOS 7 with LVM and XFS

[scottalanmiller]

In this example I will walk through the creation of a new 1TB filesystem on CentOS 7 Linux using LVM and XFS.

In my example platform, I am working from a KVM based Scale HC3 cluster. This allows me to make a VIRTIO paravirtualized block device which will show up as a /dev/vd* device in my operating system.

We can look up our available disk devices using the lsblk command:

# lsblk 
NAME                             MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0                               11:0    1   603M  0 rom  
vda                              252:0    0  14.9G  0 disk 
├─vda1                           252:1    0   500M  0 part /boot
└─vda2                           252:2    0  14.4G  0 part 
  ├─centos_lab--lnx--centos-root 253:0    0  12.9G  0 lvm  /
  └─centos_lab--lnx--centos-swap 253:1    0   1.5G  0 lvm  [SWAP]
vdb                              252:16   0 931.3G  0 disk 

We can see that /dev/vda is already in use and /dev/vdb is unused so we know that that is the new block device that we just added to our server.

Now we will add /dev/ldb to LVM as a Physical Device (PV), add it into a Volume Group (VG) and create a single Logical Volume (LV) that will span the entire device. Then comes the filesystem creation. Then we will create a new logging location at /var/log2, put an entry into /etc/fstab for the new filesystem and mount the new filesystem there.

# pvcreate /dev/vdb
  Physical volume "/dev/vdb" successfully created
# vgcreate vg_logs /dev/vdb
  Volume group "vg_logs" successfully created
# lvcreate -l 100%FREE -n lv_logs vg_logs
  Logical volume "lv_logs" created.
# mkfs.xfs /dev/vg_logs/lv_logs 
meta-data=/dev/vg_logs/lv_logs   isize=256    agcount=4, agsize=61035008 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0
data     =                       bsize=4096   blocks=244140032, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal log           bsize=4096   blocks=119209, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
# mkdir /var/log2
# echo '/dev/vg_logs/lv_logs /var/log2                                   xfs     defaults        0 0' >> /etc/fstab
# mount /var/log2
# df -h /var/log2
Filesystem                   Size  Used Avail Use% Mounted on
/dev/mapper/vg_logs-lv_logs  931G   33M  931G   1% /var/log2

That's it. We can see that the filesystem has been created and is able to be mounted via the configuration stored in /etc/fstab so that we know we are good for this to survive a reboot.

We can see our LVM details below:

# pvs
  PV         VG                    Fmt  Attr PSize   PFree 
  /dev/vda2  centos_lab-lnx-centos lvm2 a--   14.41g 40.00m
  /dev/vdb   vg_logs               lvm2 a--  931.32g     0 
# vgs
  VG                    #PV #LV #SN Attr   VSize   VFree 
  centos_lab-lnx-centos   1   2   0 wz--n-  14.41g 40.00m
  vg_logs                 1   1   0 wz--n- 931.32g     0 
# lvs
  LV      VG                    Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root    centos_lab-lnx-centos -wi-ao----  12.88g                                                    
  swap    centos_lab-lnx-centos -wi-ao----   1.49g                                                    
  lv_logs vg_logs               -wi-ao---- 931.32g  

Part of a series on Linux Systems Administration by Scott Alan Miller