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)
This article is from the "Hiyang" blog, make sure to keep this source http://hiyang.blog.51cto.com/10728919/1792812
RAID Basic Concepts