udev 可管理保存在/dev 目录下的文件、文件只有在接入相应设备后才会生成、设备被拔出后自动删除,它还允许用户添加规则、以便修
⑴ UDEV 基础
udev 可管理保存在/dev 目录下的文件、文件只有在接入相应设备后才会生成、设备被拔出后自动删除
它还允许用户添加规则、以便修改/dev中默认的名称和权限、规则保存在/etc/udev/rules.d/目录下
⑵ MySQL 绑定裸设备
只有InnoDB可以用裸设备
优点:绕过了文件系统,读写速度会有提高,,并且数据会比较安全、同时降低文件系统负担、也改善系统性能
缺点:太安全了,好多备份工具可能没法用、dd可以考虑
下面介绍如何为mysql共享表空间绑定裸设备
㈠ 制作裸设备
# fdisk /dev/sda
==> /dev/sda5
# partprobe
# fdisk -l
# pvcreate /dev/sda5
# vgcreate -s 16M mysqlvg /dev/sda5
# lvcreate -L 90M -n sharespace mysqlvg
# vim /etc/sysconfig/rawdevices
==> /dev/raw/raw1 /dev/mysqlvg/sharespace
# service rawdevices start
# chkconfig rawdevices on
# chown -R mysql:dba /dev/mapper/mysqlvg-sharespace
㈡ 配置MySQL
① 指定newraw属性
innodb_data_home_dir =
innodb_data_file_path = /dev/mapper/mysqlvg-sharespace:60Mnewraw
② 重启mysql服务,待其完成分区初始化工作后,再关闭mysql服务
③ 修改raw属性
innodb_data_home_dir =
innodb_data_file_path = /dev/mapper/mysqlvg-sharespace:60Mraw
④ 重启mysql服务
如果整个系统重启、裸设备的权限会被回收、导致mysql无法开启
官网描述如下:
will fail after the next reboot, if the /dev-tree is dynamically created by, e.g. udev, a MAKEDEV-script or similar.
After reboot, the device will regain its former permission, typically excluding access by mysql.
alert 报警如下:
130719 20:42:43 InnoDB: Operating system error number 13 in a file operation.
InnoDB: The error means mysqld does not have the access rights to
InnoDB: the directory.
InnoDB: File name /dev/mapper/mysqlvg-sharespace
InnoDB: File operation call: 'open'.
InnoDB: Cannot continue operation.
此时可选方案:
1)写个简单的初始化脚本、当重启的时候自动授权
2)配置 udev条目、
[root@odd rules.d]# pwd
/etc/udev/rules.d
[root@odd rules.d]# cat 60-raw.rules
ACTION=="add", KERNEL=="sda5", GROUP=="dba", MODE=="0660", RUN+="/bin/raw /dev/raw/raw1 %N"
[root@odd rules.d]# cat 65-raw-permissions.rules
KERNEL=="sda5", GROUP="dba", MODE="0660"
推荐阅读:
RHEL6使用UDEV修改asm磁盘名
CentOS 5上部署UDEV
InnoDB存储引擎的启动、关闭与恢复
MySQL InnoDB独立表空间的配置
MySQL Server 层和 InnoDB 引擎层 体系结构图

MySQLviewshavelimitations:1)Theydon'tsupportallSQLoperations,restrictingdatamanipulationthroughviewswithjoinsorsubqueries.2)Theycanimpactperformance,especiallywithcomplexqueriesorlargedatasets.3)Viewsdon'tstoredata,potentiallyleadingtooutdatedinforma

ProperusermanagementinMySQLiscrucialforenhancingsecurityandensuringefficientdatabaseoperation.1)UseCREATEUSERtoaddusers,specifyingconnectionsourcewith@'localhost'or@'%'.2)GrantspecificprivilegeswithGRANT,usingleastprivilegeprincipletominimizerisks.3)

MySQLdoesn'timposeahardlimitontriggers,butpracticalfactorsdeterminetheireffectiveuse:1)Serverconfigurationimpactstriggermanagement;2)Complextriggersincreasesystemload;3)Largertablesslowtriggerperformance;4)Highconcurrencycancausetriggercontention;5)M

Yes,it'ssafetostoreBLOBdatainMySQL,butconsiderthesefactors:1)StorageSpace:BLOBscanconsumesignificantspace,potentiallyincreasingcostsandslowingperformance.2)Performance:LargerrowsizesduetoBLOBsmayslowdownqueries.3)BackupandRecovery:Theseprocessescanbe

Adding MySQL users through the PHP web interface can use MySQLi extensions. The steps are as follows: 1. Connect to the MySQL database and use the MySQLi extension. 2. Create a user, use the CREATEUSER statement, and use the PASSWORD() function to encrypt the password. 3. Prevent SQL injection and use the mysqli_real_escape_string() function to process user input. 4. Assign permissions to new users and use the GRANT statement.

MySQL'sBLOBissuitableforstoringbinarydatawithinarelationaldatabase,whileNoSQLoptionslikeMongoDB,Redis,andCassandraofferflexible,scalablesolutionsforunstructureddata.BLOBissimplerbutcanslowdownperformancewithlargedata;NoSQLprovidesbetterscalabilityand

ToaddauserinMySQL,use:CREATEUSER'username'@'host'IDENTIFIEDBY'password';Here'showtodoitsecurely:1)Choosethehostcarefullytocontrolaccess.2)SetresourcelimitswithoptionslikeMAX_QUERIES_PER_HOUR.3)Usestrong,uniquepasswords.4)EnforceSSL/TLSconnectionswith

ToavoidcommonmistakeswithstringdatatypesinMySQL,understandstringtypenuances,choosetherighttype,andmanageencodingandcollationsettingseffectively.1)UseCHARforfixed-lengthstrings,VARCHARforvariable-length,andTEXT/BLOBforlargerdata.2)Setcorrectcharacters


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

SublimeText3 Chinese version
Chinese version, very easy to use

WebStorm Mac version
Useful JavaScript development tools

Zend Studio 13.0.1
Powerful PHP integrated development environment

SublimeText3 Linux new version
SublimeText3 Linux latest version

Dreamweaver CS6
Visual web development tools
