Linux Notes Day Nineth

1. RAID basic concept and mdadm implement soft raid

2, Mdadm command and bash Loop advanced

3, Linux management of LVM detailed

4, compression decompression and the use of archiving tools

One, raid:redundant array inexpensive Disks inexpensive redundant disk array.

1.1 The hard drive is connected to the motherboard via the IDE interface and cable, how can a user or system think of multiple disks as a whole, we need to use software to simulate a disk (RAID) or connect a cable to a board, The board is plugged into the motherboard (hard RAID). With the use of SCSI hard disk, disk cost is higher, no longer cheap, so the name redundant array independent disks redundant array of independent disks.

RAID level:

RAID level	Read performance	Write performance	Fault tolerant	Disk Utilization	At least the number of disks	Note
Raid0	Improve	Improve	No	N*disk	2 bucks.
Raid1	Improve	Slightly down	Yes	1*disk	2 bucks.
Raid4	Improve	Improve	Available (fixed plate)	(n-1) disk	3 bucks.	XOR or operation
Raid5	Improve	Improve	Have (take turns)	(n-1) disk	3 bucks.	Raid5+0
Raid10	Improve	Improve	Yes	N/2disk	4 bucks.	With a lot of
Raid0+1	Improve	Improve	Yes	N/2disk	4 bucks.
Raid6	Improve	Improve	Yes	(n-2) disk	4 bucks.	2-Block Check disc

Note: Due to raid4 fixed check disk, check disk pressure, poor performance, it is RAID5;RAID5 a few disk rotation check, fault-tolerant, good performance; Raid4, RAID5 can only bad a plate.

1.2 Linux 2.6 launches MDADM,MD to do soft RAID,DM (device mappen) for LVM.

Use of the Mdadm tool: MD supports organizing any device into raid, such as disks and partitions, if the SDA1 sda2 Sda3 three partitions are made RAID5, one of the partitions destroys the entire disk, so it makes no sense to raid different partitions on the same disk.

Mdadm: Modal commands

-A: Assembly mode for re-identifying previously implemented raid

-C: Create mode for creating raid

-F: monitoring mode, mail monitoring

Management mode:-f,-r,-a

-c option in Create mode:

-N #: The number of disks used to create the RAID device

-L #:raid Level

-a yes: Automatically generate device files for raid created

-C chunk_size: Soft raid self-made block size

Device files for MD devices, usually beginning with MD in the/dev directory, followed by a number;

Cat/proc/mdstat view current system to enable RAID information

For example: Create a 10G raid0.

1, create 2 partitions, and change the ID of FD 2, mdadm-c/dev/md0-a yes-n 2-l 0/dev/sd{b,c}1

3. Formatted E2FS-T ext4/dev/md0

4, mount the trial, if you want to Mount/dev/fstab,mount-a view, DF-LH view raid space

For example: Create a 10G raid5 mdadm-c/dev/md1-a yes-n 3-l 5/DEV/SDA/DEV/SDB/DEV/SDC

Linux Notes Day Nineth