Linux Practicum: Adding a Second Storage Drive on CentOS 7 with BtrFS

[scottalanmiller]

In this example I will walk through the creation of a new 1TB filesystem on CentOS 7 Linux using the BtrFS filesystem. BtrFS has both the filesystem and the logical volume manager built into a single package so we will not be using LVM here.

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.

# mkfs.btrfs /dev/vdb
btrfs-progs v3.19.1
See http://btrfs.wiki.kernel.org for more information.

Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
Turning ON incompat feature 'skinny-metadata': reduced-size metadata extent refs
fs created label (null) on /dev/vdb
	nodesize 16384 leafsize 16384 sectorsize 4096 size 931.32GiB

Mounting is now very easy:

# mkdir /var/log2
# echo '/dev/vdb	/var/log2						btrfs	defaults	0 0' >> /etc/fstab
# mount /var/log2
# df -h /var/log2
Filesystem      Size  Used Avail Use% Mounted on
/dev/vdb        932G   17M  930G   1% /var/log2

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