Linux下的lvm镜像与快照

lvm镜像(mirror)

(1)划分三个PV，其中2个PV大小要一模一样

Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xd33473f7Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         654     5253223+  83  Linux         ----5G
/dev/sdb2             655        1308     5253255   83  Linux        ----5G
/dev/sdb3            1309        1373      522112+  83  Linux       ----日志 500M

(2)把三个PV做成一个VG组

pvcreate /dev/sdb{1,2,3}Physical volume "/dev/sdb1" successfully createdPhysical volume "/dev/sdb2" successfully createdPhysical volume "/dev/sdb3" successfully createdpvsPV         VG   Fmt  Attr PSize   PFree  /dev/sdb1       lvm2 a--    5.01g   5.01g/dev/sdb2       lvm2 a--    5.01g   5.01g/dev/sdb3       lvm2 a--  509.88m 509.88vgcreate mvg /dev/sdb1 /dev/sdb2 /dev/sdb3Volume group "mvg" successfully created

(3)新建一个mirror lv卷

lvcreate -m1 -L 5G -n mlv mvgLogical volume "mlv" createdlvs -a		－－发现当前的这个LV是由三个PV组成的LV             VG   Attr       LSize Pool Origin Data%  Move Log      Cpy%Sync Convertmlv            mvg  mwi-a-m--- 5.00g                         mlv_mlog    55.62        [mlv_mimage_0] mvg  Iwi-aom--- 5.00g                                                  [mlv_mimage_1] mvg  Iwi-aom--- 5.00g                                                  [mlv_mlog]     mvg  lwi-aom--- 4.00m     

(4)测试当前mirror lv是否有镜像功能

mkfs.ext4 /dev/mvg/mlv 
mount /dev/mvg/mlv /mntrpm -q sysstat		--如果没有安装就安装下面的包
yum -y install sysstat

iostat -x 1 /dev/sda5 /dev/sda6
Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda5            143.00     0.00   33.00    0.00 22528.00     0.00   682.67     0.11    3.48   2.94   9.70
sda6              0.00   154.00    0.00   22.00     0.00 22528.00  1024.00     0.25   11.09  11.23  24.70avg-cpu:  %user   %nice %system %iowait  %steal   %idle57.07    0.00   30.81    6.06    0.00    6.06Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
sda5            144.00     0.00   32.00    0.00 22528.00     0.00   704.00     0.12    3.84   3.16  10.10
sda6              0.00   154.00    0.00   22.00     0.00 22528.00  1024.00     0.25   11.14  11.18  24.60

(5)测试镜像卷中单个PV失效

dd if=/dev/zero of=/dev/sdb1 count=1 bs=10MpvsCouldn't find device with uuid 41RfAr-mPfM-Voj0-qEfP-CCO5-AXfF-epScKO.PV             VG   Fmt  Attr PSize   PFree  /dev/sda2      vol0 lvm2 a--    7.78g 448.00m/dev/sda6      mvg  lvm2 a--    5.01g   3.01g/dev/sda7      mvg  lvm2 a--  108.00m 104.00munknown device mvg  lvm2 a-m    5.00g   3.00gvgsCouldn't find device with uuid 41RfAr-mPfM-Voj0-qEfP-CCO5-AXfF-epScKO.VG   #PV #LV #SN Attr   VSize  VFree  mvg    3   1   0 wz-pn- 10.11g   6.11gvol0   1   2   0 wz--n-  7.78g 448.00mlvs -aCouldn't find device with uuid 41RfAr-mPfM-Voj0-qEfP-CCO5-AXfF-epScKO.LV             VG   Attr     LSize   Pool Origin Data%  Move Log      Copy%  Convertmlv            mvg  mwi-a-m-   2.00g                         mlv_mlog 100.00        [mlv_mimage_0] mvg  iwi-aom-   2.00g                                                [mlv_mimage_1] mvg  iwi-aom-   2.00g                                                [mlv_mlog]     mvg  lwi-aom-   4.00m                                                home           vol0 -wi-ao-- 512.00m                                                root           vol0 -wi-ao--   6.84g      

剔除失效PV

vgreduce mvg --removemissing --forcepvsPV         VG   Fmt  Attr PSize   PFree  /dev/sda2  vol0 lvm2 a--    7.78g 448.00m/dev/sda6  mvg  lvm2 a--    5.01g   3.01g/dev/sda7  mvg  lvm2 a--  108.00m 108.00mvgsVG   #PV #LV #SN Attr   VSize VFree  mvg    2   1   0 wz--n- 5.11g   3.11gvol0   1   2   0 wz--n- 7.78g 448.00mlvs -aLV   VG   Attr     LSize   Pool Origin Data%  Move Log Copy%  Convertmlv  mvg  -wi-a---   2.00g                                           home vol0 -wi-ao-- 512.00m                                           root vol0 -wi-ao--   6.84g         

恢复后尝试重新挂载原始LV

mount /dev/mvg/mlv /mnt[root@zhou ~]# ls /mnt
file  lost+found
[root@zhou ~]# du -sh /mnt    <----数据依然存在
501M	/mnt

(6)彻底恢复带镜像功能的LV

重新新建一个PV

pvcreate /dev/sdb4vgextend mvg /dev/sda4lvconvert -m1  /dev/mvg/mlv lvs -aLV             VG   Attr     LSize   Pool Origin Data%  Move Log      Copy%  Convertmlv            mvg  mwi-aom-   5.00g                         mlv_mlog 100.00        [mlv_mimage_0] mvg  iwi-aom-   5.00g                                                [mlv_mimage_1] mvg  iwi-aom-   5.00g                                                [mlv_mlog]     mvg  lwi-aom-   4.00m          

LVM快照

1、确认卷组是否有足够的空闲空间

vgs
VG   #PV #LV #SN Attr   VSize  VFree vg     2   0   0 wz--n- 10.02g 10.02glvs				－－原始LVlv   vg   -wi-a----- 8.00g
mount  /dev/mapper/vg-lv  /mnt      

2、锁定应用保证原始LV没有数据更新，然后再新建快照

lvcreate -n lv_snap -L 100M -s /dev/vg/lv        <--100M的意思就是创建快照后,在/dev/mapper/vg-lv_snap-cow对应的设备文件(等于这里的/mnt)只能写入100M的数据,如果在没备份完之前超过100M就会导致快照失效，然而旧数据备份也就失败，只能

3、先解锁应用，然后挂载快照并且做数据备份

mount /dev/mapper/lv_snap /media
cd /media && tar cjvf /backup/test.tar.bz2 ./

4、删除快照

lvremove /dev/GLSvg/lv_snap

5、快照对应的三个设备文件

/dev/mapper/vg-lv_snap    --用于备份LV的原始数据,等于复制创建快照的时间点前的LV数据，可挂载后备份/dev/mapper/vg-lv-real      --用于对应旧数据/dev/mapper/vg-lv_snap-cow   --用于存放新写入和修改过的数据,相当于代替了原来的挂载点/mnt接收数据