本文共 9429 字,大约阅读时间需要 31 分钟。
原理:通过lvm快照给lvm真身拍个照片,当lvm真身发送改变时,lvm快照把lvm真身改变之前的内容存放在快照上,这样在lvm快照有效的这段时间内,我们看到的lvm快照上的内容始终是lvm真身在创建lvm快照时内容,通过备份lvm快照即可达到在线备份lvm真身的目的。需要注意的是,当lvm快照比lvm真身小时,若lvm真身发生的改变大于lvm快照,则lvm快照将变得无法读取而失效; 若lvm快照大于等于lvm真身,则不会发生前面的情况。
看下PE大小,lvm的大小必是PE的整数倍,为了选择合适的lvm大小,最好先检查下PE大小。
[root@server2 tune-profiles]# vgdisplay /dev/vgsrv
--- Volume group --- VG Name vgsrv System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 7 VG Access read/write VG Status resizable MAX LV 0 Cur LV 5 Open LV 4 Max PV 0 Cur PV 1 Act PV 1 VG Size 6.47 GiB PE Size 32.00 MiB Total PE 207 Alloc PE / Size 187 / 5.84 GiB Free PE / Size 20 / 640.00 MiB VG UUID Cal2wg-FWAO-4BcH-uEGX-CelP-Np5Z-fP73JW 创建base逻辑卷,大小为64M(2个PE)[root@server2 tune-profiles]# lvcreate -L 64M -n b64m /dev/vgsrv
Logical volume "b64m" created[root@server2 tune-profiles]# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert b64m vgsrv -wi-a- 64.00m home vgsrv -wi-ao 256.00m root vgsrv -wi-ao 5.00g swap vgsrv -wi-ao 544.00m格式化,挂载,并拷贝一些初始数据
[root@server2 tune-profiles]# mkfs.ext4 /dev/vgsrv/b64m mke2fs 1.41.12 (17-May-2010)Filesystem label=OS type: LinuxBlock size=1024 (log=0)Fragment size=1024 (log=0)Stride=0 blocks, Stripe width=0 blocks16384 inodes, 65536 blocks3276 blocks (5.00%) reserved for the super userFirst data block=1Maximum filesystem blocks=671088648 block groups8192 blocks per group, 8192 fragments per group2048 inodes per groupSuperblock backups stored on blocks: 8193, 24577, 40961, 57345Writing inode tables: done Creating journal (4096 blocks): doneWriting superblocks and filesystem accounting information: doneThis filesystem will be automatically checked every 38 mounts or180 days, whichever comes first. Use tune2fs -c or -i to override.[root@server2 tune-profiles]# mount /dev/vgsrv/b64m /mnt/base1/[root@server2 tune-profiles]# df -hFilesystem Size Used Avail Use% Mounted on/dev/mapper/vgsrv-root 5.0G 4.8G 0 100% /tmpfs 499M 88K 499M 1% /dev/shm/dev/vda1 248M 65M 172M 28% /boot/dev/mapper/vgsrv-home 248M 11M 226M 5% /home/dev/mapper/vgsrv-b64m 62M 5.3M 54M 9% /mnt/base1[root@server2 tune-profiles]# cp /root/* /mnt/base1/创建基于base的snap逻辑卷,两个,一个32M,一个64M。32M的用来模拟base卷变化数据大于snap卷的情况。
[root@server2 tune-profiles]# lvcreate -L 32M -s -n sb64m /dev/vgsrv/b64m
Logical volume "sb64m" created[root@server2 tune-profiles]# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert b64m vgsrv owi-ao 64.00m home vgsrv -wi-ao 256.00m root vgsrv -wi-ao 5.00g sb64m vgsrv swi-a- 32.00m b64m 0.04 swap vgsrv -wi-ao 544.00m[root@server2 tune-profiles]# lvcreate -L 64M -s -n sb64m2 /dev/vgsrv/b64m
Logical volume "sb64m2" created[root@server2 tune-profiles]# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert b64m vgsrv owi-ao 64.00m home vgsrv -wi-ao 256.00m root vgsrv -wi-ao 5.00g sb64m vgsrv swi-a- 32.00m b64m 0.09 sb64m2 vgsrv swi-a- 64.00m b64m 0.02 swap vgsrv -wi-ao 544.00m挂载两个snap卷,注意不能在snap上再创建文件系统,如果snap卷格式化后再挂载上去看到的将只是一个空的文件系统。
[root@server2 tune-profiles]# mkdir /mnt/sbase1
[root@server2 tune-profiles]# mkdir /mnt/sbase2[root@server2 tune-profiles]# mount /dev/vgsrv/sb64m /mnt/sbase1/[root@server2 tune-profiles]# ll /mnt/sbase1/total 166-rw-------. 1 root root 4354 Jan 7 22:17 anaconda-ks.cfg-rw-------. 1 root root 5352 Jan 7 22:17 cachegrind.out.4206-rw-------. 1 root root 5354 Jan 7 22:17 cachegrind.out.4207-rw-r--r--. 1 root root 45581 Jan 7 22:17 install.log-rw-r--r--. 1 root root 10075 Jan 7 22:17 install.log.syslogdrwx------. 2 root root 12288 Jan 7 22:16 lost+found-rw-r--r--. 1 root root 57074 Jan 7 22:17 post.log-rw-r--r--. 1 root root 289 Jan 7 22:17 pre.log-rw-r--r--. 1 root root 6 Jan 7 22:17 root-rw-r--r--. 1 root root 5614 Jan 7 22:17 zcav.HDD-rw-r--r--. 1 root root 3094 Jan 7 22:17 zcav.png-rw-r--r--. 1 root root 2334 Jan 7 22:17 zcav.SSD[root@server2 tune-profiles]# mount /dev/vgsrv/sb64m2 /mnt/sbase2/[root@server2 tune-profiles]# ll /mnt/sbase2/total 166-rw-------. 1 root root 4354 Jan 7 22:17 anaconda-ks.cfg-rw-------. 1 root root 5352 Jan 7 22:17 cachegrind.out.4206-rw-------. 1 root root 5354 Jan 7 22:17 cachegrind.out.4207-rw-r--r--. 1 root root 45581 Jan 7 22:17 install.log-rw-r--r--. 1 root root 10075 Jan 7 22:17 install.log.syslogdrwx------. 2 root root 12288 Jan 7 22:16 lost+found-rw-r--r--. 1 root root 57074 Jan 7 22:17 post.log-rw-r--r--. 1 root root 289 Jan 7 22:17 pre.log-rw-r--r--. 1 root root 6 Jan 7 22:17 root-rw-r--r--. 1 root root 5614 Jan 7 22:17 zcav.HDD-rw-r--r--. 1 root root 3094 Jan 7 22:17 zcav.png-rw-r--r--. 1 root root 2334 Jan 7 22:17 zcav.SSD[root@server2 tune-profiles]# df -hFilesystem Size Used Avail Use% Mounted on/dev/mapper/vgsrv-root 5.0G 4.8G 0 100% /tmpfs 499M 88K 499M 1% /dev/shm/dev/vda1 248M 65M 172M 28% /boot/dev/mapper/vgsrv-home 248M 11M 226M 5% /home/dev/mapper/vgsrv-b64m 62M 5.4M 54M 10% /mnt/base1/dev/mapper/vgsrv-sb64m 62M 5.4M 54M 10% /mnt/sbase1/dev/mapper/vgsrv-sb64m2 62M 5.4M 54M 10% /mnt/sbase2[root@server2 tune-profiles]# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert b64m vgsrv owi-ao 64.00m home vgsrv -wi-ao 256.00m root vgsrv -wi-ao 5.00g sb64m vgsrv swi-ao 32.00m b64m 0.10 sb64m2 vgsrv swi-ao 64.00m b64m 0.02 swap vgsrv -wi-ao 544.00m [root@server2 tune-profiles]# cat /mnt/sbase1/root base1[root@server2 tune-profiles]# cat /mnt/sbase2/root base1模拟base继续处理业务,业务数据大于32M小于64M
[root@server2 tune-profiles]# dd if=/dev/zero of=/mnt/base1/40M.img bs=40M count=11+0 records in1+0 records out41943040 bytes (42 MB) copied, 0.763238 s, 55.0 MB/s[root@server2 tune-profiles]# df -hFilesystem Size Used Avail Use% Mounted on/dev/mapper/vgsrv-root 5.0G 4.8G 0 100% /tmpfs 499M 88K 499M 1% /dev/shm/dev/vda1 248M 65M 172M 28% /boot/dev/mapper/vgsrv-home 248M 11M 226M 5% /home/dev/mapper/vgsrv-b64m 62M 46M 14M 78% /mnt/base1/dev/mapper/vgsrv-sb64m 62M 5.4M 54M 10% /mnt/sbase1/dev/mapper/vgsrv-sb64m2 62M 5.4M 54M 10% /mnt/sbase2发现32M的snap卷已经无法读取
[root@server2 tune-profiles]# cat /mnt/base1/root base1#比较奇怪的是这里还能读到文件,刚开始猜测读的是缓存,但是后面又做了几次实验发现drop掉缓存还是能读取,反而只要lvs列出的Snap%为100时,百分之百无法读取,现在想想应该是有延时或者base卷的change没做成功
[root@server2 tune-profiles]# cat /mnt/sbase1/root base1[root@server2 tune-profiles]# cat /mnt/sbase2/root base1[root@server2 tune-profiles]# cd /mnt/sbase1/[root@server2 sbase1]# lltotal 0[root@server2 sbase1]# ls -lhtotal 0[root@server2 sbase1]# ls -a. ..[root@server2 sbase1]# cd ..[root@server2 mnt]# cd sbase2/[root@server2 sbase2]# touch sbase2[root@server2 sbase2]# lltotal 167-rw-------. 1 root root 4354 Jan 7 22:17 anaconda-ks.cfg-rw-------. 1 root root 5352 Jan 7 22:17 cachegrind.out.4206-rw-------. 1 root root 5354 Jan 7 22:17 cachegrind.out.4207-rw-r--r--. 1 root root 45581 Jan 7 22:17 install.log-rw-r--r--. 1 root root 10075 Jan 7 22:17 install.log.syslogdrwx------. 2 root root 12288 Jan 7 22:16 lost+found-rw-r--r--. 1 root root 57074 Jan 7 22:17 post.log-rw-r--r--. 1 root root 289 Jan 7 22:17 pre.log-rw-r--r--. 1 root root 6 Jan 7 22:17 root-rw-r--r--. 1 root root 0 Jan 7 22:22 sbase2-rw-r--r--. 1 root root 5614 Jan 7 22:17 zcav.HDD-rw-r--r--. 1 root root 3094 Jan 7 22:17 zcav.png-rw-r--r--. 1 root root 2334 Jan 7 22:17 zcav.SSD[root@server2 sbase2]# cd ../base1/[root@server2 base1]# touch base1[root@server2 base1]# lltotal 41129-rw-r--r--. 1 root root 41943040 Jan 7 22:21 40M.img-rw-------. 1 root root 4354 Jan 7 22:17 anaconda-ks.cfg-rw-r--r--. 1 root root 0 Jan 7 22:22 base1-rw-------. 1 root root 5352 Jan 7 22:17 cachegrind.out.4206-rw-------. 1 root root 5354 Jan 7 22:17 cachegrind.out.4207-rw-r--r--. 1 root root 45581 Jan 7 22:17 install.log-rw-r--r--. 1 root root 10075 Jan 7 22:17 install.log.syslogdrwx------. 2 root root 12288 Jan 7 22:16 lost+found-rw-r--r--. 1 root root 57074 Jan 7 22:17 post.log-rw-r--r--. 1 root root 289 Jan 7 22:17 pre.log-rw-r--r--. 1 root root 6 Jan 7 22:17 root-rw-r--r--. 1 root root 5614 Jan 7 22:17 zcav.HDD-rw-r--r--. 1 root root 3094 Jan 7 22:17 zcav.png-rw-r--r--. 1 root root 2334 Jan 7 22:17 zcav.SSD[root@server2 base1]# ll ../sbase2/total 167-rw-------. 1 root root 4354 Jan 7 22:17 anaconda-ks.cfg-rw-------. 1 root root 5352 Jan 7 22:17 cachegrind.out.4206-rw-------. 1 root root 5354 Jan 7 22:17 cachegrind.out.4207-rw-r--r--. 1 root root 45581 Jan 7 22:17 install.log-rw-r--r--. 1 root root 10075 Jan 7 22:17 install.log.syslogdrwx------. 2 root root 12288 Jan 7 22:16 lost+found-rw-r--r--. 1 root root 57074 Jan 7 22:17 post.log-rw-r--r--. 1 root root 289 Jan 7 22:17 pre.log-rw-r--r--. 1 root root 6 Jan 7 22:17 root-rw-r--r--. 1 root root 0 Jan 7 22:22 sbase2-rw-r--r--. 1 root root 5614 Jan 7 22:17 zcav.HDD-rw-r--r--. 1 root root 3094 Jan 7 22:17 zcav.png-rw-r--r--. 1 root root 2334 Jan 7 22:17 zcav.SSD[root@server2 base1]# lvs /dev/vgsrv/sb64m: read failed after 0 of 4096 at 67043328: Input/output error /dev/vgsrv/sb64m: read failed after 0 of 4096 at 67100672: Input/output error /dev/vgsrv/sb64m: read failed after 0 of 4096 at 0: Input/output error /dev/vgsrv/sb64m: read failed after 0 of 4096 at 4096: Input/output error LV VG Attr LSize Origin Snap% Move Log Copy% Convert b64m vgsrv owi-ao 64.00m home vgsrv -wi-ao 256.00m root vgsrv -wi-ao 5.00g sb64m vgsrv Swi-I- 32.00m b64m 100.00 sb64m2 vgsrv swi-ao 64.00m b64m 62.90 swap vgsrv -wi-ao 544.00m [root@server2 base1]# 本文实际与下文有很大重叠:[实验]通过lvm快照进行热备 http://blog.csdn.net/t0nsha/article/details/7752743