11.8. btrfs

11.8. btrfs
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yum install btrfs-progs

# mkfs.btrfs /dev/sdb1

指定卷標

# mkfs.btrfs /dev/sdb2 -L /backup

11.8.1. Mount Btrfs

# mkdir /mnt/btrfs
# mount /dev/sdb1 /mnt/btrfs

查看掛載是否成功

# df -Th
Filesystem    Type    Size  Used Avail Use% Mounted on
/dev/sda1     ext4     49G   15G   32G  32% /
tmpfs        tmpfs     32G  264K   32G   1% /dev/shm
/dev/sda3     ext4     52G  1.3G   48G   3% /var
/dev/sdb1    btrfs    2.0T   14G  2.0T   1% /mnt/btrfs

 針對 SSD 的優化:
# mount –t btrfs –o SSD /dev/sda5 /btrfsdisk


打開壓縮功能：
# mount –t btrfs –o compress /dev/sda5 /btrfsdisk

11.8.1.1. Mount Snap

mount -t btrfs -o subvol=your_snapshot /dev/sdb2 /mnt/snap

mount -t btrfs -o subvol=aaa /dev/md127p5 /mnt/snap

11.8.1.2. fstab

11.8.1.2.1. btrfs-show

[root@r610 ~]# btrfs-show
Label: none  uuid: 0b097eeb-1f0b-476a-955b-52122ef42bfc
        Total devices 1 FS bytes used 13.03GB
        devid    1 size 2.00TB used 24.04GB path /dev/sdb1

Btrfs Btrfs v0.19

11.8.1.2.2. /etc/fstab

UUID=0b097eeb-1f0b-476a-955b-52122ef42bfc /opt    btrfs   defaults 1 2

11.8.2. Snapshots and subvolumes (快照與子卷管理)

11.8.2.1. subvolumes

# df -T
Filesystem     Type  1K-blocks      Used Available Use% Mounted on
/dev/md126p2   ext4   50395844  19952780  27883064  42% /
tmpfs          tmpfs   4024944       800   4024144   1% /dev/shm
/dev/md126p1   ext4     495844    172140    298104  37% /boot
/dev/md126p6   btrfs 500084736 360835636 119893924  76% /opt
/dev/md126p5   btrfs 409600000  24927332 368284612   7% /www

# btrfs subvolume create /www/git
Create subvolume '/www/git'

# btrfs subvolume list /www
ID 641 gen 21351 top level 5 path git

fstab 掛在子卷

$ cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Thu Oct 18 13:53:45 2012
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=88ec1ccf-7d8d-4107-a143-1ed0ec64a572 /                       ext4    defaults        1 1
UUID=c0786771-1c85-45be-a9ab-ef3ee16fccb4 /boot                   ext4    defaults        1 2
UUID=e1b89740-21f0-4507-97e9-a658cd7d3716 /opt                    btrfs   defaults        1 2
UUID=76e46795-ebaf-4d2d-8996-1e15979bf3c8 /www                    btrfs   defaults        1 2
UUID=76e46795-ebaf-4d2d-8996-1e15979bf3c8 /home/git               btrfs   defaults,subvol=git        1 2
UUID=c578f1b3-4bbe-4f48-b3d3-3929c65cb99c swap                    swap    defaults        0 0
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

11.8.2.2.

創建快照
# btrfs subvolume snapshot /www /www/backup_2012
查看快照
# btrfs subvolume list -a /www
掛在快照
# mount -t btrfs -o subvol=backup_2012 /dev/md127p5 /mnt/snap
刪除快照
# btrfs subvolume delete /www/backup_2012
Delete subvolume '/www/backup_2012'

11.8.3. btrfsctl

11.8.3.1. Resizes the filesystem

11.8.3.2. Snapshot

Btrfs v0.19

# touch /mnt/btrfs/test1
# touch /mnt/btrfs/test2
# ls /mnt/btrfs/test?
/mnt/btrfs/test1  /mnt/btrfs/test2

# echo 'This is a test' > /mnt/btrfs/test1
# btrfsctl –s snap1 /mnt/btrfs
#vi test1
 Test1 is modified
#cd /mnt/btrfs/snap1
#cat test1
 This is a test

11.8.4. btrfs-vol

# btrfs-vol –a /dev/sdc1 /mnt/btrfs

11.8.5. btrfs-convert

btrfs-convert /dev/sdb1

11.8.6. btrfsck

# btrfsck /dev/sdb1
found 13994164224 bytes used err is 0
total csum bytes: 13588316
total tree bytes: 79728640
total fs tree bytes: 28860416
btree space waste bytes: 10282024
file data blocks allocated: 13931024384
 referenced 13906980864
Btrfs Btrfs v0.19

11.8.7. btrfs-debug-tree

[root@r610 ~]# btrfs-debug-tree /dev/sdb1 |head
root tree
leaf 49463296 items 9 free space 2349 generation 298 owner 1
fs uuid 0b097eeb-1f0b-476a-955b-52122ef42bfc
chunk uuid 2826f868-c775-4835-8690-1020a2a9fbf5
        item 0 key (EXTENT_TREE ROOT_ITEM 0) itemoff 3756 itemsize 239
                root data bytenr 49446912 level 2 dirid 0 refs 1
        item 1 key (DEV_TREE ROOT_ITEM 0) itemoff 3517 itemsize 239
                root data bytenr 36139008 level 0 dirid 0 refs 1
        item 2 key (FS_TREE INODE_REF 6) itemoff 3500 itemsize 17
                inode ref index 0 namelen 7 name: default

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