Linux note0x01

RAID & LVM

RAID

RAID

1. RAID0

RAID0 splits (“stripes”) data evenly across two or more disks, without parity information, redundancy, or fault tolerance.

1. RAID1

RAID 1 consists of an exact copy (or mirror) of a set of data on two or more disks; a classic RAID 1 mirrored pair contains two disks.

1. RAID5

RAID 5 consists of block-level striping with distributed parity. Unlike in RAID 4, parity information is distributed among the drives. It requires that all drives but one be present to operate. Upon failure of a single drive, subsequent reads can be calculated from the distributed parity such that no data is lost. RAID 5 requires at least three disks

1. RAID1+0

RAID 01, also called RAID 0+1, is a RAID level using a mirror of stripes, achieving both replication and sharing of data between disks.

Mdadm command

Example: RAID1+0

• mdadm -Cv /dev/md0 -a yes -n 4 -l 10 /dev/sdb /dev/sdc /dev/sdd /dev/sde

  • C create a RAID card

  • v verbose, display the process

  • a automanticly create dev file

  • n number of use disk

  • l plan 10 means RAID1+0

• formatting: mkfs.ext4 /dev/md0

• mkdir /RAID & mount /dev/md0 /RAID & df -h

• mdadm -D /dev/md0 view the detail info

Damage to Disk Array & Repair

1. Simulate dev damage: mdadm /dev/md0 -f /dev/sdb

2. RAID 1+0: It will not be effected if only one RAID disk failed. Just use mdadm to replace it.

   • umount /RAID every operation about raid umount first

   • madam /dev/md0 -a /dev/sdb add new /dev/sdb

3. Disk Array + backup-disk

Extrame：Both of disk from RAID 1 were damaged.

Solution: backup-disk

mdadm -Cv /dev/md0 -n 3 -l 5 -x 1 /dev/sdb /dev/sdc /dev/sdd /dev/sde
- x backup-disk /dev/sde

LVM: Logical Volume Manager

Note: extend or shrink volume

功能 物理卷管理 卷组管理 逻辑卷管理 扫描 pvscan vgscan lvscan 建立 pvcreate vgcreate lvcreate 显示 pvdisplay vgdisplay lvdisplay 删除 pvremove vgremove lvremove 扩展 vgextend lvextend 缩小 vgreduce lvreduce

Deploy

1. support /sdb & /sdc with lvm pvcreate /dev/sdb /dev/sdc

2. Add both of them into storage and check them vgcreate storage /dev/sdb /dev/sdc & vgdisplay

3. split a logical volume dev about 150MB size lvcreate -n vo -l 37 storage & lvdisplay

4. formatting and mount it to use. mkdfs.ext4 /dev/storage/vo & mount /dev/storage/vo /mountDir

5. check info and make it effect permantly echo "/dev/storage/vo /mountDir ext4 defaults 0 0" >> /etc/fstab

Extend logical volume

1. umount /mountDir before extend umount it

2. lvextend -L 290M /dev/storgage/vo extend it to 290MB

3. Check disk intergrity e2fsck -f /dev/storage/vo

4. Resize disk resize2fs /dev/storage/vo

5. Remount and df -h

Shrink logical volume

1. umount /mountDir before shrink umount it

2. e2fsck -f /dev/storage/vo check sys intergrity

3. resize2fs /dev/storage/vo 120M shrink it to 120MB

4. Remount mount -a & df -h

Snapshot

1. View volume group vgdisplay

2. lvcreate -L 120M -s -n SNAP /dev/storage/vo

   • s:create a snap group

   • L: size

3. Do something…

4. umount /mountDir & lvconvert --merge /dev/storage/SNAP Recover operation(will be deleted after that)

LVM Delete

1. umount /mountDir & vim /etc/fstab

2. lvremove /dev/storage/vo delete logical dev

3. vgremove storage delete volume group

4. pvremove /dev/sdb /dev/sdc delete physics group dev