Software raid 5, software raid
Implementation of Software raid 5
RAID 5 is a storage solution that combines storage performance, data security, and storage costs. RAID 5 can be understood as a compromise between RAID 0 and RAID 1. RAID 5 can provide data security for the system, but it is more secure than Mirror, and the disk space utilization is higher than Mirror. RAID 5 has a Data Reading Speed similar to RAID 0, but has an additional parity information. The data writing speed is slightly slower than that of a single disk. At the same time, because multiple pieces of data correspond to one parity information, the disk space utilization of RAID 5 is higher than that of RAID 1, and the storage cost is relatively low. This is a solution that is widely used at present.
1 partition
Here, two hard disks are used:/dev/sda8 and/dev/sda9, And/dev/sdb and/dev/sdc.
Note: Change the partition ID to fd.
2 create raid 5
mdadm -C /dev/md5 -a yes -l 5 -n 3 -x 1 /dev/sdd1 /dev/sde1 /dev/sdf /dev/sdb2
[root@centos7 ~]# mdadm -C /dev/md5 -a yes -l 5 -n 3 -x 1 /dev/sda8 /dev/sda9 /dev/sdb /dev/sdcmdadm: Defaulting to version 1.2 metadatamdadm: array /dev/md5 started.
-C Creation Mode
-N #: Use # Fast devices to create RAID
-L #: indicates the level of the RAID to be created.
-A {yes | no}: automatically creates the device file of the target RAID device.
-C CHUNK_SIZE: indicates the block size.
-X #: specifies the number of backup disks. The default value is the number of backup disks.
3. Create a File System
[root@centos7 ~]# mkfs.ext4 /dev/md5
4 Mount
(1) create a mount directory
[root@centos7 ~]# mkdir /mnt/raid5
(2) Mounting
[root@centos7 ~]# mount /dev/md5 /mnt/raid5
5. Generate a configuration file
[root@centos7 ~]# cat /etc/mdadm.confARRAY /dev/md5 metadata=1.2 spares=1 name=centos7.3.loacl:5 UUID=5ec4115c:ab1e25c8:ff36d8a2:74f6fd8a
View the md status
[root@centos7 ~]# cat /proc/mdstatPersonalities : [raid0] [raid6] [raid5] [raid4]md5 : active raid5 sdb[4] sdc[3](S) sda9[1] sda8[0]2095104 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
View raid details
[root@centos7 ~]# mdadm -D /dev/md5/dev/md5:Version : 1.2Creation Time : Tue Apr 25 14:38:54 2017Raid Level : raid5Array Size : 2095104 (2046.00 MiB 2145.39 MB)Used Dev Size : 1047552 (1023.00 MiB 1072.69 MB)Raid Devices : 3Total Devices : 4Persistence : Superblock is persistentUpdate Time : Tue Apr 25 14:50:08 2017State : cleanActive Devices : 3Working Devices : 4Failed Devices : 0Spare Devices : 1Layout : left-symmetricChunk Size : 512KName : centos7.3.loacl:5 (local to host centos7.3.loacl)UUID : 5ec4115c:ab1e25c8:ff36d8a2:74f6fd8aEvents : 18Number Major Minor RaidDevice State0 8 8 0 active sync /dev/sda81 8 9 1 active sync /dev/sda94 8 16 2 active sync /dev/sdb3 8 32 - spare /dev/sdc
You can see the expected combination of three active devices and one idle (standby) device.
6. Disable and enable
umount /mnt/raid0mdadm -S /dev/md0mdadm -A /dev/md0
(1) Disable raid
[root@centos7 ~]# umount /mnt/raid5[root@centos7 ~]# mdadm -S /dev/md5mdadm: stopped /dev/md5
Check that the instance has been stopped successfully.
[root@centos7 ~]# mdadm -D /dev/md5mdadm: cannot open /dev/md5: No such file or directory
(2) Enable raid Devices
[root@centos7 ~]# mdadm -A /dev/md5mdadm: /dev/md5 has been started with 3 drives and 1 spare.
Check again and find that the instance has been started successfully.
[root@centos7 ~]# cat /proc/mdstatPersonalities : [raid0] [raid6] [raid5] [raid4]md5 : active raid5 sda8[0] sdc[3](S) sdb[4] sda9[1]2095104 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
7 simulate/dev/sdc corruption
[root@centos7 ~]# mdadm /dev/md5 -f /dev/sdcmdadm: set /dev/sdc faulty in /dev/md5
8 Remove/dev/sdc
[Root @ centos7 ~] # Mdadm/dev/md5-r/dev/sdcmdadm: hot removed/dev/sdc from/dev/md5 [root @ centos7 ~] # Mdadm-D/dev/md5/dev/md5: […] Active Devices: 3 Working Devices: 3 Failed Devices: 0 Spare Devices: 0 […] Number Major Minor RaidDevice State0 8 8 0 active sync/dev/sda81 8 9 1 active sync/dev/sda94 8 16 2 active sync/dev/sdb
You can see that the removal is successful.
Let's take a look at the disk situation.
[root@centos7 ~]# lsblkNAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTfd0 2:0 1 4K 0 disksda 8:0 0 20G 0 disk[……]├─sda8 8:8 0 1G 0 part│ └─md5 9:5 0 2G 0 raid5└─sda9 8:9 0 1G 0 part└─md5 9:5 0 2G 0 raid5sdb 8:16 0 1G 0 disk└─md5 9:5 0 2G 0 raid5sdc 8:32 0 1G 0 disksr0 11:0 1 7.7G 0 rom
We can see that/dev/sdc is no longer an md5 array.
9 add to a raid Member
[root@centos7 ~]# mdadm /dev/md5 -a /dev/sdcmdadm: added /dev/sdc
[root@centos7 ~]# mdadm -D /dev/md5/dev/md5:[……]Raid Devices : 3Total Devices : 4Active Devices : 3Working Devices : 4[……]Number Major Minor RaidDevice State0 8 8 0 active sync /dev/sda81 8 9 1 active sync /dev/sda94 8 16 2 active sync /dev/sdb3 8 32 - spare /dev/sdc
You can see that the instance is successfully added.
10 increase the number of raid members from 3 to 4
Add the device/dev/sdd to the array.
[root@centos7 ~]# mdadm -G /dev/md5 -n 4 -a /dev/sddmdadm: added /dev/sddmdadm: Need to backup 3072K of critical section..
Check file system integrity
[root@centos7 ~]# e2fsck -f /dev/md5e2fsck 1.42.9 (28-Dec-2013)Pass 1: Checking inodes, blocks, and sizesPass 2: Checking directory structurePass 3: Checking directory connectivityPass 4: Checking reference countsPass 5: Checking group summary information/dev/md5: 11/131072 files (0.0% non-contiguous), 17964/523776 blocks
Synchronize file systems
[root@centos7 ~]# resize2fs /dev/md5resize2fs 1.42.9 (28-Dec-2013)Resizing the filesystem on /dev/md5 to 785664 (4k) blocks.The filesystem on /dev/md5 is now 785664 blocks long.
Check the/dev/md5 array.
[root@centos7 ~]# mdadm -D /dev/md5/dev/md5:Version : 1.2Creation Time : Tue Apr 25 14:38:54 2017Raid Level : raid5Array Size : 3142656 (3.00 GiB 3.22 GB)Used Dev Size : 1047552 (1023.00 MiB 1072.69 MB)Raid Devices : 4Total Devices : 5Persistence : Superblock is persistentUpdate Time : Tue Apr 25 15:13:32 2017State : cleanActive Devices : 4Working Devices : 5Failed Devices : 0Spare Devices : 1 Layout : left-symmetricChunk Size : 512KName : centos7.3.loacl:5 (local to host centos7.3.loacl)UUID : 5ec4115c:ab1e25c8:ff36d8a2:74f6fd8aEvents : 47Number Major Minor RaidDevice State0 8 8 0 active sync /dev/sda81 8 9 1 active sync /dev/sda94 8 16 2 active sync /dev/sdb5 8 48 3 active sync /dev/sdd3 8 32 - spare /dev/sdc