From 2e755abf31633af0dc1da59f6bf5d8ca4c05d248 Mon Sep 17 00:00:00 2001 From: shipsw Date: Fri, 6 Feb 2015 14:36:02 +0800 Subject: [PATCH 1/2] Delete 20140917 How to create a software RAID-1 array with mdadm on Linux.md --- ...ftware RAID-1 array with mdadm on Linux.md | 225 ------------------ 1 file changed, 225 deletions(-) delete mode 100644 sources/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md diff --git a/sources/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md b/sources/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md deleted file mode 100644 index bab7cfbcb2..0000000000 --- a/sources/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md +++ /dev/null @@ -1,225 +0,0 @@ -Translating by shipsw - -How to create a software RAID-1 array with mdadm on Linux -================================================================================ -Redundant Array of Independent Disks (RAID) is a storage technology that combines multiple hard disks into a single logical unit to provide fault-tolerance and/or improve disk I/O performance. Depending on how data is stored in an array of disks (e.g., with striping, mirroring, parity, or any combination thereof), different RAID levels are defined (e.g., RAID-0, RAID-1, RAID-5, etc). RAID can be implemented either in software or with a hardware RAID card. On modern Linux, basic software RAID functionality is available by default. - -In this post, we'll discuss the software setup of a RAID-1 array (also known as a "mirroring" array), where identical data is written to the two devices that form the array. While it is possible to implement RAID-1 with partitions on a single physical hard drive (as with other RAID levels), it won't be of much use if that single hard drive fails. In fact, that's why most RAID levels normally use multiple physical drives to provide redundancy. In the event of any single drive failure, the virtual RAID block device should continue functioning without issues, and allow us to replace the faulty drive without significant production downtime and, more importantly, with no data loss. However, it does not replace the need to save periodic system backups in external storage. - -Since the actual storage capacity (size) of a RAID-1 array is the size of the smallest drive, normally (if not always) you will find two identical physical drives in RAID-1 setup. - -### Installing mdadm on Linux ### - -The tool that we are going to use to create, assemble, manage, and monitor our software RAID-1 is called mdadm (short for **m**ultiple **d**isks **adm**in). On Linux distros such as Fedora, CentOS, RHEL or Arch Linux, mdadm is available by default. On Debian-based distros, mdadm can be installed with aptitude or apt-get. - -#### Fedora, CentOS or RHEL #### - -As mdadm comes pre-installed, all you have to do is to start RAID monitoring service, and configure it to auto-start upon boot: - - # systemctl start mdmonitor - # systemctl enable mdmonitor - -For CentOS/RHEL 6, use these commands instead: - - # service mdmonitor start - # chkconfig mdmonitor on - -#### Debian, Ubuntu or Linux Mint #### - -On Debian and its derivatives, mdadm can be installed with **aptitude or apt-get**: - - # aptitude install mdadm - -On Ubuntu, you will be asked to configure postfix MTA for sending out email notifications (as part of RAID monitoring). You can skip it for now. - -On Debian, the installation will start with the following explanatory message to help us decide whether or not we are going to install the root filesystem on a RAID array. What we need to enter on the next screen will depend on this decision. Read it carefully: - -![](https://farm4.staticflickr.com/3918/15220883382_c14eb95914_z.jpg) - -Since we will not use our RAID-1 for the root filesystem, we will leave the answer blank: - -![](https://farm6.staticflickr.com/5555/15198241896_29e08b977f.jpg) - -When asked whether we want to start (reassemble) our array automatically during each boot, choose "Yes". Note that we will need to add an entry to the /etc/fstab file later in order for the array to be properly mounted during the boot process as well. - -![](https://farm4.staticflickr.com/3875/15220883342_2b1d689a0a_z.jpg) - -### Partitioning Hard Drives ### - -Now it's time to prepare the physical devices that will be used in our array. For this setup, I have plugged in two 8 GB USB drives that have been identified as /dev/sdb and /dev/sdc from dmesg output: - - # dmesg | less - ----------- - -[ 60.014863] sd 3:0:0:0: [sdb] 15826944 512-byte logical blocks: (8.10 GB/7.54 GiB) -[ 75.066466] sd 4:0:0:0: [sdc] 15826944 512-byte logical blocks: (8.10 GB/7.54 GiB) - -We will use fdisk to create a primary partition on each disk that will occupy its entire size. The following steps show how to perform this task on /dev/sdb, and assume that this drive hasn't been partitioned yet (otherwise, we can delete the existing partition(s) to start off with a clean disk): - - # fdisk /dev/sdb - -Press 'p' to print the current partition table: - -![](https://farm4.staticflickr.com/3883/15198241836_24625edcf3_z.jpg) - -(if one or more partitions are found, they can be deleted with 'd' option. Then 'w' option is used to apply the changes). - -Since no partitions are found, we will create a new primary partition ['n'] as a primary partition ['p'], assign the partition number = ['1'] to it, and then indicate its size. You can press Enter key to accept the proposed default values, or enter a value of your choosing, as shown in the image below. - -![](https://farm4.staticflickr.com/3875/15034475369_7e72fb9f2e_z.jpg) - -Now repeat the same process for /dev/sdc. - -If we have two drives of different sizes, say 750 GB and 1 TB for example, we should create a primary partition of 750 GB on each of them, and use the remaining space on the bigger drive for another purpose, independent of the RAID array. - -### Create a RAID-1 Array ### - -Once you are done with creating the primary partition on each drive, use the following command to create a RAID-1 array: - - # mdadm -Cv /dev/md0 -l1 -n2 /dev/sdb1 /dev/sdc1 - -Where: - -- **-Cv**: creates an array and produce verbose output. -- **/dev/md0**: is the name of the array. -- **-l1** (l as in "level"): indicates that this will be a RAID-1 array. -- **-n2**: indicates that we will add two partitions to the array, namely /dev/sdb1 and /dev/sdc1. - -The above command is equivalent to: - - # mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1 - -If alternatively you want to add a spare device in order to replace a faulty disk in the future, you can add '--spare-devices=1 /dev/sdd1' to the above command. - -Answer "y" when prompted if you want to continue creating an array, then press Enter: - -![](https://farm4.staticflickr.com/3894/15034569970_709bd51718.jpg) - -You can check the progress with the following command: - - # cat /proc/mdstat - -![](https://farm6.staticflickr.com/5565/15221267975_701b819e6d_z.jpg) - -Another way to obtain more information about a RAID array (both while it's being assembled and after the process is finished) is: - - # mdadm --query /dev/md0 - # mdadm --detail /dev/md0 (or mdadm -D /dev/md0) - -![](https://farm6.staticflickr.com/5583/15034683868_6c28564e5a_z.jpg) - -Of the information provided by 'mdadm -D', perhaps the most useful is that which shows the state of the array. The active state means that there is currently I/O activity happening. Other possible states are clean (all I/O activity has been completed), degraded (one of the devices is faulty or missing), resyncing (the system is recovering from an unclean shutdown such as a power outage), or recovering (a new drive has been added to the array, and data is being copied from the other drive onto it), to name the most common states. - -### Formatting and Mounting a RAID Array ### - -The next step is formatting (with ext4 in this example) the array: - - # mkfs.ext4 /dev/md0 - -![](https://farm4.staticflickr.com/3849/15034683838_01e34e7196_z.jpg) - -Now let's mount the array, and verify that it was mounted correctly: - - # mount /dev/md0 /mnt - # mount - -![](https://farm6.staticflickr.com/5554/15034696167_c4fc907c8e_z.jpg) - -### Monitor a RAID Array ### - -The mdadm tool comes with RAID monitoring capability built in. When mdadm is set to run as a daemon (which is the case with our RAID setup), it periodically polls existing RAID arrays, and reports on any detected events via email notification or syslog logging. Optionally, it can also be configured to invoke contingency commands (e.g., retrying or removing a disk) upon detecting any critical errors. - -By default, mdadm scans all existing partitions and MD arrays, and logs any detected event to /var/log/syslog. Alternatively, you can specify devices and RAID arrays to scan in mdadm.conf located in /etc/mdadm/mdadm.conf (Debian-based) or /etc/mdadm.conf (Red Hat-based), in the following format. If mdadm.conf does not exist, create one. - - DEVICE /dev/sd[bcde]1 /dev/sd[ab]1 - - ARRAY /dev/md0 devices=/dev/sdb1,/dev/sdc1 - ARRAY /dev/md1 devices=/dev/sdd1,/dev/sde1 - ..... - - # optional email address to notify events - MAILADDR your@email.com - -After modifying mdadm configuration, restart mdadm daemon: - -On Debian, Ubuntu or Linux Mint: - - # service mdadm restart - -On Fedora, CentOS/RHEL 7: - - # systemctl restart mdmonitor - -On CentOS/RHEL 6: - - # service mdmonitor restart - -### Auto-mount a RAID Array ### - -Now we will add an entry in the /etc/fstab to mount the array in /mnt automatically during boot (you can specify any other mount point): - - # echo "/dev/md0 /mnt ext4 defaults 0 2" << /etc/fstab - -To verify that mount works okay, we now unmount the array, restart mdadm, and remount. We can see that /dev/md0 has been mounted as per the entry we just added to /etc/fstab: - - # umount /mnt - # service mdadm restart (on Debian, Ubuntu or Linux Mint) - or systemctl restart mdmonitor (on Fedora, CentOS/RHEL7) - or service mdmonitor restart (on CentOS/RHEL6) - # mount -a - -![](https://farm6.staticflickr.com/5563/15218183681_63a10da704_z.jpg) - -Now we are ready to access the RAID array via /mnt mount point. To test the array, we'll copy the /etc/passwd file (any other file will do) into /mnt: - -![](https://farm6.staticflickr.com/5593/15034475219_a3476aec0a_o.png) - -On Debian, we need to tell the mdadm daemon to automatically start the RAID array during boot by setting the AUTOSTART variable to true in the /etc/default/mdadm file: - - AUTOSTART=true - -### Simulating Drive Failures ### - -We will simulate a faulty drive and remove it with the following commands. Note that in a real life scenario, it is not necessary to mark a device as faulty first, as it will already be in that state in case of a failure. - -First, unmount the array: - - # umount /mnt - -Now, notice how the output of 'mdadm -D /dev/md0' indicates the changes after performing each command below. - - # mdadm /dev/md0 --fail /dev/sdb1 #Marks /dev/sdb1 as faulty - # mdadm --remove /dev/md0 /dev/sdb1 #Removes /dev/sdb1 from the array - -Afterwards, when you have a new drive for replacement, re-add the drive again: - - # mdadm /dev/md0 --add /dev/sdb1 - -The data is then immediately started to be rebuilt onto /dev/sdb1: - -![](https://farm4.staticflickr.com/3855/15221267875_dfc6af8804_z.jpg) - -Note that the steps detailed above apply for systems with hot-swappable disks. If you do not have such technology, you will also have to stop a current array, and shutdown your system first in order to replace the part: - - # mdadm --stop /dev/md0 - # shutdown -h now - -Then add the new drive and re-assemble the array: - - # mdadm /dev/md0 --add /dev/sdb1 - # mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 - -Hope this helps. - --------------------------------------------------------------------------------- - -via: http://xmodulo.com/2014/09/create-software-raid1-array-mdadm-linux.html - -作者：[Gabriel Cánepa][a] -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出 - -[a]:http://xmodulo.com/author/gabriel From d09b7e88245af9f68f989bfc259fd88b239709ec Mon Sep 17 00:00:00 2001 From: shipsw Date: Fri, 6 Feb 2015 14:40:44 +0800 Subject: [PATCH 2/2] Create 20140917 How to create a software RAID-1 array with mdadm on Linux.md --- ...ftware RAID-1 array with mdadm on Linux.md | 223 ++++++++++++++++++ 1 file changed, 223 insertions(+) create mode 100644 translated/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md diff --git a/translated/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md b/translated/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md new file mode 100644 index 0000000000..ddbdfc8689 --- /dev/null +++ b/translated/tech/20140917 How to create a software RAID-1 array with mdadm on Linux.md @@ -0,0 +1,223 @@ +如何使用linux程序mdadm创建软件RAID1软阵列 +================================================================================ +磁盘冗余阵列(RAID)是将多个物理磁盘结合成一个逻辑磁盘的技术，该技术可以提高磁盘容错性能，提高磁盘的读写速度。根据数据存储的排列(如 条带存储，镜像存储，奇偶或者他们的组合)，定义了几个不同级别的RAID(RAID-0，RAID-1，RAID-5 等等)。磁盘阵列可以使用软件或者硬件方式实现。现代Linux操作系统中，基本的软件RAID功能是默认安装的。 + +本文中，我们将介绍软件方式构建RAID-1阵列(镜像阵列)，RAID-1将相同的数据写到不同的设备中。虽然可以使用同一个磁盘的两个分区实现RAID-1，但是如果磁盘坏了的话数据就都丢了，所以没什么意义。实际上，这也是为什么大多数RAID级别都使用多个物理磁盘提供冗余。当单盘失效后不影响整个阵列的运行，并且可以在线更换磁盘，最重要的是数据不会丢失。尽管如此，阵列不能取代外部存储的定期备份。 + +由于RAID-1阵列的大小是最小磁盘的大小，一般来说应该使用两个大小相同的磁盘来组建RAID-1。 + +### 安装mdadm ### + +我们将使用mdadm（简称多盘管理）工具创建、组装、管理和监控软件RAID-1。在诸如Fedora、CentOS、RHEL或者Arch Linux 的发行版中，mdadm是默认安装的。在基于Debian的发行版中，可以使用aptitude 或者 apt-get 安装mdadm。 + +#### Fedora, CentOS 或 RHEL #### + +由于adadm是预装的，所以我们只需要开启RAID守护服务，并将其配置成开机启动即可： + + # systemctl start mdmonitor + # systemctl enable mdmonitor + +对于CentOS/RHEL 6系统，使用以下命令： + + # service mdmonitor start + # chkconfig mdmonitor on + +#### Debian, Ubuntu 或 Linux Mint #### + +在Debian或类Debian系统中，mdadm可以使用 **aptitude 或者 apt-get** 安装： + + # aptitude install mdadm + +Ubuntu系统中，会要求为电子邮件通知配置后缀MTA。你可以跳过去。 + +Debian系统中，安装程序会显示以下解释信息，用来帮助我们去判断是否将根目录安装到RAID阵列中。下面的所有操作都有赖于这一步，所以应该仔细阅读他。 + +![](https://farm4.staticflickr.com/3918/15220883382_c14eb95914_z.jpg) + +我们不在根目录使用RAID-1，所以留空。 + +![](https://farm6.staticflickr.com/5555/15198241896_29e08b977f.jpg) + +提示是否开机启动阵列的时候，选择是。注意，这里需要往/etc/fstab 文件中添加一个条目使得系统启动的时候正确挂载阵列。 + +![](https://farm4.staticflickr.com/3875/15220883342_2b1d689a0a_z.jpg) + +### 硬盘分区 ### + +现在开始准备建立阵列需要的硬盘。这里往插入两个8GB的usb磁盘，使用dmesg命令设备显示设备 /dev/sdb 和 /dev/sdc + + # dmesg | less + +---------- + +[ 60.014863] sd 3:0:0:0: [sdb] 15826944 512-byte logical blocks: (8.10 GB/7.54 GiB) +[ 75.066466] sd 4:0:0:0: [sdc] 15826944 512-byte logical blocks: (8.10 GB/7.54 GiB) + +我们使用fdisk为每个磁盘建立一个大小为8G的主分区。以下步骤是如何在/dev/sdb上建立分区，假设次磁盘从未被分区(如果有其他分区的话，可以删掉)： + + # fdisk /dev/sdb + +按p键输出现在的分区表： + +![](https://farm4.staticflickr.com/3883/15198241836_24625edcf3_z.jpg) + +(如果有分区的话，可以使用 d 选项删除，w 选项应用更改)。 + +磁盘上没有分区，所以我们使用命令 ['n'] 创建一个主分区['p'], 分配分区号为['1'] 并且指定大小。你可以按回车使用默认值，或者输入一个你想设置的值。如下图： + +![](https://farm4.staticflickr.com/3875/15034475369_7e72fb9f2e_z.jpg) + +用同样的方法为/dev/sdc 分区。 + +如果我们有两个不同容量的硬盘，比如 750GB 和 1TB的话，我们需要在每个磁盘上分出一个750GB的主分区，大盘剩下的空间可以用作他用，不加入磁盘阵列。 + +### 创建 RAID-1 阵列 ### + +磁盘分区完成后，我们可以使用以下命令创建 RAID-1 阵列： + + # mdadm -Cv /dev/md0 -l1 -n2 /dev/sdb1 /dev/sdc1 + +说明： + +- **-Cv**: 创建一个阵列并打印出详细信息。 +- **/dev/md0**: 阵列名称。 +- **-l1** (l as in "level"): 指定阵列类型为 RAID-1 。 +- **-n2**: 指定我们将两个分区加入到阵列中去，分别为/dev/sdb1 和 /dev/sdc1 + +以上命令和下面的等价: + + # mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1 + +如果你想在在磁盘失效时添加另外一个磁盘到阵列中，可以指定 '--spare-devices=1 /dev/sdd1' 到以上命令。 + +输入 “y” 继续创建阵列，回车： + +![](https://farm4.staticflickr.com/3894/15034569970_709bd51718.jpg) + +可以使用以下命令查看进度： + + # cat /proc/mdstat + +![](https://farm6.staticflickr.com/5565/15221267975_701b819e6d_z.jpg) + +另外一个获取阵列信息的方法是： + + # mdadm --query /dev/md0 + # mdadm --detail /dev/md0 (or mdadm -D /dev/md0) + +![](https://farm6.staticflickr.com/5583/15034683868_6c28564e5a_z.jpg) + +'mdadm -D'命令提供的信息中，最重要就是阵列状态类。激活状态说明阵列正在进行读写操作。其他几个状态分别为 完成(读写完成)、降级(有一块磁盘失效或丢失)或者恢复中(一张新盘已插入，系统正在写入数据)。这几个状态涵盖类大多数情况。 + +### 格式化或加载磁盘阵列 ### + +下一步就是格式化阵列了，本例中使用ext4格式： + + # mkfs.ext4 /dev/md0 + +![](https://farm4.staticflickr.com/3849/15034683838_01e34e7196_z.jpg) + +现在可以加载阵列并验证其正常加载： + + # mount /dev/md0 /mnt + # mount + +![](https://farm6.staticflickr.com/5554/15034696167_c4fc907c8e_z.jpg) + +### 监控磁盘阵列 ### + +mdadm工具内置有磁盘阵列监控功能。当mdadm作为守护程序运行的时候(就像我们上文那样)，会周期性的检测阵列运行状态，将检测到的信息通过电子邮件或者系统日志报告上来。当然，也可以配置其在发生致命性错误的时候调用紧急命令。 + +mdadm默认会记录所有已知分区和阵列的事件，并将他们记录到 /var/log/syslog中。或者你可以在配置文件中(/etc/mdadm/mdadm.conf debian系统 /etc/mdadm.conf 红帽子系统)以以下格式指定监控设备或者阵列。如果mdadm.conf文件不存在，你可以创建一个。 + + DEVICE /dev/sd[bcde]1 /dev/sd[ab]1 + + ARRAY /dev/md0 devices=/dev/sdb1,/dev/sdc1 + ARRAY /dev/md1 devices=/dev/sdd1,/dev/sde1 + ..... + + # optional email address to notify events + MAILADDR your@email.com + +编辑完毕mdadm配置文件后，重启mdadm服务： + +Debian系统，Ubuntu或者Linux Mint: + + # service mdadm restart + +Fedora, CentOS 或 RHEL 7: + + # systemctl restart mdmonitor + +CentOS或者RHEL 6: + + # service mdmonitor restart + +### 自动加载阵列 ### + +现在我们在/etc/fstab中加入条目使得系统启动的时候将阵列挂载到/mnt目录下： + + # echo "/dev/md0 /mnt ext4 defaults 0 2" << /etc/fstab + +为了验证挂载脚本工作正常，我们首先卸载阵列，重启mdadm，然后重新加载。可以看到/dev/md0已经安装我们添加到/etc/fstab中的条目加载了： + + # umount /mnt + # service mdadm restart (on Debian, Ubuntu or Linux Mint) + or systemctl restart mdmonitor (on Fedora, CentOS/RHEL7) + or service mdmonitor restart (on CentOS/RHEL6) + # mount -a + +![](https://farm6.staticflickr.com/5563/15218183681_63a10da704_z.jpg) + +现在我们的阵列已经可以访问类，拷贝文件/etc/passwd到/mnt中测试一下： + +![](https://farm6.staticflickr.com/5593/15034475219_a3476aec0a_o.png) + +Debian系统中，需要在/etc/default/mdadm 设置 AUTOSTART 变量为 true 才能使mdadm守护程序在开机时自动加载阵列： + + AUTOSTART=true + +### 模拟磁盘丢失故障 ### + +我们将使用以下命令卸载磁盘来模拟磁盘故障。注意，在实际应用中，磁盘已经上故障状态了，不需要卸载。 + +首先，卸载阵列： + + # umount /mnt + +现在注意每次执行命令后 'mdadm -D /dev/md0' 的输出。 + + # mdadm /dev/md0 --fail /dev/sdb1 #Marks /dev/sdb1 as faulty + # mdadm --remove /dev/md0 /dev/sdb1 #Removes /dev/sdb1 from the array + +然后，如果你有个备用盘的话，重新添加以下： + + # mdadm /dev/md0 --add /dev/sdb1 + +数据会被自动添加到备用盘 /dev/sdb1 上： + +![](https://farm4.staticflickr.com/3855/15221267875_dfc6af8804_z.jpg) + +注意以上所述步骤只适合支持磁盘热拔插的系统，在不支持热拔插的系统中，还是得停止阵列并关机后更换备用盘： + + # mdadm --stop /dev/md0 + # shutdown -h now + +最后将新驱动器重新添加到阵列中： + + # mdadm /dev/md0 --add /dev/sdb1 + # mdadm --assemble /dev/md0 /dev/sdb1 /dev/sdc1 + +希望本文对你有所帮助 + +-------------------------------------------------------------------------------- + +via: http://xmodulo.com/2014/09/create-software-raid1-array-mdadm-linux.html + +作者：[Gabriel Cánepa][a] +译者：[shipsw](https://github.com/shipsw) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出 + +[a]:http://xmodulo.com/author/gabriel