RAID Basic Concepts

1 How does the process access files on the hard disk?

The process initiates a system call (the process runs on the CPU) and the kernel issues instructions to control the memory load file (the kernel is running on the CPU) -the process reads the file from memory (the process runs on the CPU)

Only one process can run on the CPU (single core), so this process involves processes and cores using CPU resources in turn.

2 What is a driver?

Converts the control instruction of the CPU into an operation instruction that the device can perform.

Drivers are generally provided by hardware manufacturers, but also the public version of the drive;

The performance of the public drive may not be as good as that provided by the hardware vendor;

3 RAID Development

sled:single Large expensive disk, single high-capacity disks, fast speed

raid:reduncdant Arrays of inexpensive Disks, inexpensive redundant disk array

raid:reduncdant Arrays of independent Disks, independent redundant disk array

4 Strip Technology

When the data is transferred in storage, it is not in block, but the larger data blocks are stored in the same location on different disks, and the transmission capacity is enhanced .

5 RAID level

Level only means disk is organized differently

0: Strip

Advantage: Read and write performance increase n times disadvantage: no redundancy capability

1: Mirror

Advantages: Write performance degradation, read performance improvement, redundancy capability disadvantage: Wasted disk

5: cyclic redundancy check

Advantages: Improved read and write performance with redundancy capability

: Mirror + stripe

: Stripe + mirror

6 disk mirroring technology, mirror

Ensure data availability, but waste disk space

7 Check Code Technology

Cyclic redundancy check code is stored separately

8 JBOD

connect multiple disks to 1 disk, no performance boost, no redundancy

9 HDD Interface

IDE (ATA): Integrated Drive Electronics, electronic integrated driver

speed:130mb/s, parallel

SATA 3:serial Advanced Technology Attachment

Speed: 600mb/s, 7200rpm,revolutions Per Minute, Serial

Scsi:small computer System Interface, small PC input/output interface

speed:320mb/s, parallel

Sas:serial attached SCSI, serial additional SCSI

Speed:200mb/s, serial, 15000rpm

USB 3.0:universal Serial Bus, universal Serial bus

speed:400mb/s, serial

SSD: solidState disk, SSD

Sequential reading and writing ability, random reading and writing ability, but for the mechanical hard disk sequence and random read and write have improved

RAID type

Hardware RAID

With the BIOS configuration RAID controller, RAID is recognized by the operating system as/DEV/SDA,/DEV/SDB,

raid drivers may be required during installation of the operating system, or RAID disks will not be recognized

Some RAID controllers have their own cpu/memory/battery, the CPU first deposits the data into the raid memory, and the RAID controller writes the data to the disk

Software RAID, logical raid

The kernel supports RAID, requires MD (multi disks) module support, MD simulates the RAID controller, implements the software simulation hardware

/dev/md#, identifying different raid devices

Set disk to FD format, will store some raid metadata on disk, if the operating system is damaged, re-install the operating system, after scanning can recover data

    

From for notes (Wiz)

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RAID Basic Concepts