Linux btrfs文件系统及管理
[root@localhost ~]# btrfs fi df /btrfs/
Data, RAID1: total=1.00GiB, used=320.00KiB #对比上面改为了raid1
System, RAID1: total=32.00MiB, used=16.00KiB
Metadata, RAID1: total=256.00MiB, used=112.00KiB
GlobalReserve, single: total=16.00MiB, used=0.00B
[root@localhost ~]#
显示当前文件系统使用信息
bash/shell Code复制内容到剪贴板
[root@localhost btrfs]# btrfs fi usage /btrfs/
Overall:
Device size: 37.00GiB #总的空间
Device allocated: 2.56GiB #分给元数据管理区的空间
Device unallocated: 34.44GiB #未分出去的
Device missing: 0.00B
Used: 896.00KiB #使用了的空间
Free (estimated): 18.22GiB(min: 18.22GiB) #可用空间，这里因是raid1 镜像卷
Data ratio: 2.00
Metadata ratio: 2.00
Global reserve: 16.00MiB(used: 0.00B)
Data,RAID1: Size:1.00GiB, Used:320.00KiB
/dev/sdb 1.00GiB
/dev/sdc 1.00GiB
Metadata,RAID1: Size:256.00MiB, Used:112.00KiB
/dev/sdb 256.00MiB
/dev/sdc 256.00MiB
System,RAID1: Size:32.00MiB, Used:16.00KiB
/dev/sdb 32.00MiB
/dev/sdc 32.00MiB
Unallocated:
/dev/sdb 15.72GiB #这里2各磁盘 分配的空间不同，可以说明btrfs的内建raid1不是按物理盘划分的，而是按chunk，
/dev/sdc 18.72GiB #可以看到具体某块磁盘的使用状况。
[root@localhost btrfs]# btrfs device stats /btrfs/ #查看磁盘错误信息
[/dev/sdb].write_io_errs 0
[/dev/sdb].read_io_errs 0
[/dev/sdb].flush_io_errs 0
[/dev/sdb].corruption_errs 0
[/dev/sdb].generation_errs 0
[/dev/sdc].write_io_errs 0
[/dev/sdc].read_io_errs 0
[/dev/sdc].flush_io_errs 0
[/dev/sdc].corruption_errs 0
[/dev/sdc].generation_errs 0
[root@localhost btrfs]# btrfs device usage /btrfs/ #磁盘的空间使用状态
/dev/sdb, ID: 1
Device size: 20.00GiB
Data,RAID1: 1.00GiB
Metadata,RAID1: 256.00MiB
System,RAID1: 32.00MiB
Unallocated: 15.72GiB
/dev/sdc, ID: 2
Device size: 20.00GiB
Data,RAID1: 1.00GiB
Metadata,RAID1: 256.00MiB
System,RAID1: 32.00MiB
Unallocated: 18.72GiB
压缩测试
[root@localhost btrfs22]# du -sh /btrfs /btrfs22
5.1G/btrfs
5.1G/btrfs22
[root@localhost btrfs22]# btrfs fi show
Label: 'btrfs' uuid: 2a9f0d3d-f8a0-4757-9f4e-d1efa04a683a
Total devices 2 FS bytes used 178.63MiB #btrfs挂载采用lzo压缩，空间被压缩，因是文本文档压缩效果很明显。
devid 1 size 17.00GiB used 1.28GiB path /dev/sdb
devid 2 size 20.00GiB used 1.28GiB path /dev/sdc
Label: 'btrfs22' uuid: d4da4497-b82e-4846-b51c-cd7127ff5c74
Total devices 2 FS bytes used 5.01GiB #btrfs22挂载没有启用压缩功能。
devid 1 size 20.00GiB used 4.04GiB path /dev/sdd
devid 2 size 20.00GiB used 4.00GiB path /dev/sde
btrfs-progs v3.19.1
子卷和快照的管理
bash/shell Code复制内容到剪贴板
btrfs subvolume
[root@localhost btrfs22]# btrfs subvolume create /btrfs/btrfs.sub #创建子卷
Create subvolume '/btrfs/btrfs.sub'
[root@localhost btrfs22]# btrfs subvolume list /btrfs #显示子卷
ID 259 gen 43 top level 5 path btrfs.sub
[root@localhost btrfs22]# umount /btrfs
[root@localhost ~]# mount -o subvol=btrfs.sub /dev/sdc /btrfs.sub/ #单独挂载子卷
[root@localhost ~]# btrfs subvolume show /btrfs.sub/
/btrfs.sub
Name: btrfs.sub
uuid: 811deb2f-764f-6440-899c-cddb2b9867e2
Parent uuid: -
Creation time: 2016-05-11 08:43:51
Object ID: 259
Generation (Gen): 43
Gen at creation: 43
Parent: 5
Top Level: 5
Flags: -
Snapshot(s):
子卷删除
bash/shell Code复制内容到剪贴板
[root@localhost ~]# umount /btrfs.sub/ #卸卸载子卷
[root@localhost ~]# btrfs subvolume delete /btrfs/btrfs.sub
#执行删除命令
[root@localhost ~]# btrfs subvolume list /btrfs
#查看 已经被删除
ID 260 gen 45 top level 5 path btrfs.sub22
子卷快照，类似创建子卷
bash/shell Code复制内容到剪贴板
[root@localhost ~]# btrfs subvolume list /btrfs
ID 260 gen 45 top level 5 path btrfs.sub22
[root@localhost ~]# btrfs subvolume snapshot /btrfs/btrfs.sub22/ /btrfs/btrfs.sub22_snapshot
Create a snapshot of '/btrfs/btrfs.sub22/' in '/btrfs/btrfs.sub22_snapshot'
[root@localhost ~]# btrfs subvolume list /btrfs
ID 260 gen 50 top level 5 path btrfs.sub22
ID 262 gen 50 top level 5 path btrfs.sub22_snapshot
单个文件快照
bash/shell Code复制内容到剪贴板
[root@localhost btrfs]# cp --relink hostname hostname_snap
cp: unrecognized option '--relink'
Try 'cp --help' for more information.
[root@localhost btrfs]# cp --reflink hostname hostname_snap
[root@localhost btrfs]# cp --reflink hostname hostname_snap^C
[root@localhost btrfs]# echo "magedu.com" >> hostname
[root@localhost btrfs]# cat hostname
localhost.localdomain
magedu.com
[root@localhost btrfs]# cat hostname_snap
localhost.localdomain
[root@localhost btrfs]#
ext文件系统转换为btrfs
bash/shell Code复制内容到剪贴板
[root@localhost ~]# cp -r /tmp/* /sdf/
[root@localhost ~]# cd /sdf/
[root@localhost sdf]# ls
ks-script-OqV4Gb lost+found yum.log
[root@localhost ~]# umount /sdf/ #第一步，先卸载需要转换的ext分区
[root@localhost ~]# fsck -f /dev/sdf #第二步，强制检测磁盘
fsck from util-linux 2.23.2
e2fsck 1.42.9 (28-Dec-2013)
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/sdf: 13/1310720 files (0.0% non-contiguous), 126323/5242880 blocks
[root@localhost ~]# btrfs-convert /dev/sdf #第三步，执行转换命令
creating btrfs metadata.
copy inodes [o] [ 0/ 13]
creating ext2fs image file.
cleaning up system chunk.
conversion complete.
[root@localhost ~]# mount /dev/sdf /sdf/
[root@localhost ~]# cd /sdf/
[root@localhost sdf]# ls
ext2_saved ks-script-OqV4Gb lost+found yum.log #转换产生的ext2_saved，不可删除，删除就无法转回ext文件系统
[root@localhost sdf]# cat ks-script-OqV4Gb #转换后查看文件正常。
restorecon -ir /etc/sysconfig/network-scripts /var/lib /etc/lvm \
/dev /etc/iscsi /var/lib/iscsi /root /var/lock /var/log \
/etc/modprobe.d /etc/sysconfig /var/cache/yum
# Also relabel the OSTree variants of the normal mounts (if they exist)
restorecon -ir /var/roothome /var/home /var/opt /var/srv /var/media /var/mnt
restorecon -i /etc/rpm/macros /etc/dasd.conf /etc/zfcp.conf /lib64 /usr/lib64 \
/etc/blkid.tab* /etc/mtab /etc/fstab /etc/resolv.conf \
/etc/modprobe.conf* /var/log/*tmp /etc/crypttab \
/etc/mdadm.conf /etc/sysconfig/network /root/install.log* \
/etc/*shadow* /etc/dhcp/dhclient-*.conf /etc/localtime \
/etc/hostname /root/install.log*
if [ -e /etc/zipl.conf ]; then
restorecon -i /etc/zipl.conf
fi
[root@localhost sdf]# blkid /dev/sdf
/dev/sdf: UUID="20bd2176-28d9-49fb-88e9-b746f5ea2736" UUID_SUB="9076e700-22a2-420e-81df-feb79449ab7c" TYPE="btrfs" #查看文件系统，已经变为btrfs
btrfs转回ext3
[root@localhost ~]# umount /sdf/ #第一步，卸载
[root@localhost ~]# btrfs-convert -r /dev/sdf #第二步，执行转换命令
rollback complete.
[root@localhost ~]# blkid /dev/sdf
/dev/sdf: UUID="8d6c4b81-9602-428a-a340-f01b176fa82b" SEC_TYPE="ext2" TYPE="ext3" #查看转换结果，已经变为etx3格式。
[root@localhost ~]#
总结：初步了解btrfs，首先，扩展性基于B-tree架构，单个文件，磁盘，文件个数，大大超过现在对扩展性的要求，其次，数据一致性，基于COW和checksum确保数据正常(btrfs的数据检测，修复，恢复相关的命令操作后面补充)，再次，设备管理功能强大，内建raid,联机raid调整，联机空间扩展和缩减，联机物理卷增删，快照，子卷，可脱离raid和lvm.
【Linux btrfs文件系统及管理】相关文章：