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部分翻译完成 RAID series
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struggling 翻译中
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Introduction to RAID, Concepts of RAID and RAID Levels – Part 1
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================================================================================
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RAID is a Redundant Array of Inexpensive disks, but nowadays it is called Redundant Array of Independent drives. Earlier it is used to be very costly to buy even a smaller size of disk, but nowadays we can buy a large size of disk with the same amount like before. Raid is just a collection of disks in a pool to become a logical volume.
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Understanding RAID Setups in Linux
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Raid contains groups or sets or Arrays. A combine of drivers make a group of disks to form a RAID Array or RAID set. It can be a minimum of 2 number of disk connected to a raid controller and make a logical volume or more drives can be in a group. Only one Raid level can be applied in a group of disks. Raid are used when we need excellent performance. According to our selected raid level, performance will differ. Saving our data by fault tolerance & high availability.
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This series will be titled Preparation for the setting up RAID ‘s through Parts 1-9 and covers the following topics.
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- Part 1: Introduction to RAID, Concepts of RAID and RAID Levels
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- Part 2: How to setup RAID0 (Stripe) in Linux
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- Part 3: How to setup RAID1 (Mirror) in Linux
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- Part 4: How to setup RAID5 (Striping with Distributed Parity) in Linux
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- Part 5: How to setup RAID6 (Striping with Double Distributed Parity) in Linux
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- Part 6: Setting Up RAID 10 or 1+0 (Nested) in Linux
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- Part 7: Growing an Existing RAID Array and Removing Failed Disks in Raid
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- Part 8: Recovering (Rebuilding) failed drives in RAID
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- Part 9: Managing RAID in Linux
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This is the Part 1 of a 9-tutorial series, here we will cover the introduction of RAID, Concepts of RAID and RAID Levels that are required for the setting up RAID in Linux.
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### Software RAID and Hardware RAID ###
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Software RAID have low performance, because of consuming resource from hosts. Raid software need to load for read data from software raid volumes. Before loading raid software, OS need to get boot to load the raid software. No need of Physical hardware in software raids. Zero cost investment.
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Hardware RAID have high performance. They are dedicated RAID Controller which is Physically built using PCI express cards. It won’t use the host resource. They have NVRAM for cache to read and write. Stores cache while rebuild even if there is power-failure, it will store the cache using battery power backups. Very costly investments needed for a large scale.
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Hardware RAID Card will look like below:
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Hardware RAID
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#### Featured Concepts of RAID ####
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- Parity method in raid regenerate the lost content from parity saved information’s. RAID 5, RAID 6 Based on Parity.
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- Stripe is sharing data randomly to multiple disk. This won’t have full data in a single disk. If we use 3 disks half of our data will be in each disks.
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- Mirroring is used in RAID 1 and RAID 10. Mirroring is making a copy of same data. In RAID 1 it will save the same content to the other disk too.
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- Hot spare is just a spare drive in our server which can automatically replace the failed drives. If any one of the drive failed in our array this hot spare drive will be used and rebuild automatically.
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- Chunks are just a size of data which can be minimum from 4KB and more. By defining chunk size we can increase the I/O performance.
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RAID’s are in various Levels. Here we will see only the RAID Levels which is used mostly in real environment.
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- RAID0 = Striping
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- RAID1 = Mirroring
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- RAID5 = Single Disk Distributed Parity
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- RAID6 = Double Disk Distributed Parity
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- RAID10 = Combine of Mirror & Stripe. (Nested RAID)
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RAID are managed using mdadm package in most of the Linux distributions. Let us get a Brief look into each RAID Levels.
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#### RAID 0 (or) Striping ####
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Striping have a excellent performance. In Raid 0 (Striping) the data will be written to disk using shared method. Half of the content will be in one disk and another half will be written to other disk.
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Let us assume we have 2 Disk drives, for example, if we write data “TECMINT” to logical volume it will be saved as ‘T‘ will be saved in first disk and ‘E‘ will be saved in Second disk and ‘C‘ will be saved in First disk and again ‘M‘ will be saved in Second disk and it continues in round-robin process.
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In this situation if any one of the drive fails we will loose our data, because with half of data from one of the disk can’t use to rebuilt the raid. But while comparing to Write Speed and performance RAID 0 is Excellent. We need at least minimum 2 disks to create a RAID 0 (Striping). If you need your valuable data don’t use this RAID LEVEL.
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- High Performance.
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- There is Zero Capacity Loss in RAID 0
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- Zero Fault Tolerance.
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- Write and Reading will be good performance.
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#### RAID 1 (or) Mirroring ####
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Mirroring have a good performance. Mirroring can make a copy of same data what we have. Assuming we have two numbers of 2TB Hard drives, total there we have 4TB, but in mirroring while the drives are behind the RAID Controller to form a Logical drive Only we can see the 2TB of logical drive.
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While we save any data, it will write to both 2TB Drives. Minimum two drives are needed to create a RAID 1 or Mirror. If a disk failure occurred we can reproduce the raid set by replacing a new disk. If any one of the disk fails in RAID 1, we can get the data from other one as there was a copy of same content in the other disk. So there is zero data loss.
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- Good Performance.
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- Here Half of the Space will be lost in total capacity.
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- Full Fault Tolerance.
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- Rebuilt will be faster.
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- Writing Performance will be slow.
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- Reading will be good.
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- Can be used for operating systems and database for small scale.
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#### RAID 5 (or) Distributed Parity ####
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RAID 5 is mostly used in enterprise levels. RAID 5 work by distributed parity method. Parity info will be used to rebuild the data. It rebuilds from the information left on the remaining good drives. This will protect our data from drive failure.
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Assume we have 4 drives, if one drive fails and while we replace the failed drive we can rebuild the replaced drive from parity informations. Parity information’s are Stored in all 4 drives, if we have 4 numbers of 1TB hard-drive. The parity information will be stored in 256GB in each drivers and other 768GB in each drives will be defined for Users. RAID 5 can be survive from a single Drive failure, If drives fails more than 1 will cause loss of data’s.
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- Excellent Performance
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- Reading will be extremely very good in speed.
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- Writing will be Average, slow if we won’t use a Hardware RAID Controller.
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- Rebuild from Parity information from all drives.
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- Full Fault Tolerance.
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- 1 Disk Space will be under Parity.
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- Can be used in file servers, web servers, very important backups.
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#### RAID 6 Two Parity Distributed Disk ####
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RAID 6 is same as RAID 5 with two parity distributed system. Mostly used in a large number of arrays. We need minimum 4 Drives, even if there 2 Drive fails we can rebuild the data while replacing new drives.
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Very slower than RAID 5, because it writes data to all 4 drivers at same time. Will be average in speed while we using a Hardware RAID Controller. If we have 6 numbers of 1TB hard-drives 4 drives will be used for data and 2 drives will be used for Parity.
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- Poor Performance.
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- Read Performance will be good.
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- Write Performance will be Poor if we not using a Hardware RAID Controller.
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- Rebuild from 2 Parity Drives.
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- Full Fault tolerance.
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- 2 Disks space will be under Parity.
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- Can be Used in Large Arrays.
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- Can be use in backup purpose, video streaming, used in large scale.
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#### RAID 10 (or) Mirror & Stripe ####
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RAID 10 can be called as 1+0 or 0+1. This will do both works of Mirror & Striping. Mirror will be first and stripe will be the second in RAID 10. Stripe will be the first and mirror will be the second in RAID 01. RAID 10 is better comparing to 01.
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Assume, we have 4 Number of drives. While I’m writing some data to my logical volume it will be saved under All 4 drives using mirror and stripe methods.
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If I’m writing a data “TECMINT” in RAID 10 it will save the data as follow. First “T” will write to both disks and second “E” will write to both disk, this step will be used for all data write. It will make a copy of every data to other disk too.
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Same time it will use the RAID 0 method and write data as follow “T” will write to first disk and “E” will write to second disk. Again “C” will write to first Disk and “M” to second disk.
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- Good read and write performance.
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- Here Half of the Space will be lost in total capacity.
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- Fault Tolerance.
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- Fast rebuild from copying data.
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- Can be used in Database storage for high performance and availability.
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### Conclusion ###
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In this article we have seen what is RAID and which levels are mostly used in RAID in real environment. Hope you have learned the write-up about RAID. For RAID setup one must know about the basic Knowledge about RAID. The above content will fulfil basic understanding about RAID.
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In the next upcoming articles I’m going to cover how to setup and create a RAID using Various Levels, Growing a RAID Group (Array) and Troubleshooting with failed Drives and much more.
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--------------------------------------------------------------------------------
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via: http://www.tecmint.com/understanding-raid-setup-in-linux/
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作者：[Babin Lonston][a]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:http://www.tecmint.com/author/babinlonston/
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@ -1,219 +0,0 @@
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struggling 翻译中
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Creating Software RAID0 (Stripe) on ‘Two Devices’ Using ‘mdadm’ Tool in Linux – Part 2
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================================================================================
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RAID is Redundant Array of Inexpensive disks, used for high availability and reliability in large scale environments, where data need to be protected than normal use. Raid is just a collection of disks in a pool to become a logical volume and contains an array. A combine drivers makes an array or called as set of (group).
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RAID can be created, if there are minimum 2 number of disk connected to a raid controller and make a logical volume or more drives can be added in an array according to defined RAID Levels. Software Raid are available without using Physical hardware those are called as software raid. Software Raid will be named as Poor man raid.
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Setup RAID0 in Linux
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Main concept of using RAID is to save data from Single point of failure, means if we using a single disk to store the data and if it’s failed, then there is no chance of getting our data back, to stop the data loss we need a fault tolerance method. So, that we can use some collection of disk to form a RAID set.
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#### What is Stripe in RAID 0? ####
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Stripe is striping data across multiple disk at the same time by dividing the contents. Assume we have two disks and if we save content to logical volume it will be saved under both two physical disks by dividing the content. For better performance RAID 0 will be used, but we can’t get the data if one of the drive fails. So, it isn’t a good practice to use RAID 0. The only solution is to install operating system with RAID0 applied logical volumes to safe your important files.
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- RAID 0 has High Performance.
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- Zero Capacity Loss in RAID 0. No Space will be wasted.
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- Zero Fault Tolerance ( Can’t get back the data if any one of disk fails).
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- Write and Reading will be Excellent.
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#### Requirements ####
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Minimum number of disks are allowed to create RAID 0 is 2, but you can add more disk but the order should be twice as 2, 4, 6, 8. If you have a Physical RAID card with enough ports, you can add more disks.
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Here we are not using a Hardware raid, this setup depends only on Software RAID. If we have a physical hardware raid card we can access it from it’s utility UI. Some motherboard by default in-build with RAID feature, there UI can be accessed using Ctrl+I keys.
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If you’re new to RAID setups, please read our earlier article, where we’ve covered some basic introduction of about RAID.
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- [Introduction to RAID and RAID Concepts][1]
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**My Server Setup**
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Operating System : CentOS 6.5 Final
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IP Address : 192.168.0.225
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Two Disks : 20 GB each
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This article is Part 2 of a 9-tutorial RAID series, here in this part, we are going to see how we can create and setup Software RAID0 or striping in Linux systems or servers using two 20GB disks named sdb and sdc.
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### Step 1: Updating System and Installing mdadm for Managing RAID ###
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1. Before setting up RAID0 in Linux, let’s do a system update and then install ‘mdadm‘ package. The mdadm is a small program, which will allow us to configure and manage RAID devices in Linux.
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# yum clean all && yum update
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# yum install mdadm -y
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Install mdadm Tool
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### Step 2: Verify Attached Two 20GB Drives ###
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2. Before creating RAID 0, make sure to verify that the attached two hard drives are detected or not, using the following command.
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# ls -l /dev | grep sd
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Check Hard Drives
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3. Once the new hard drives detected, it’s time to check whether the attached drives are already using any existing raid with the help of following ‘mdadm’ command.
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# mdadm --examine /dev/sd[b-c]
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Check RAID Devices
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In the above output, we come to know that none of the RAID have been applied to these two sdb and sdc drives.
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### Step 3: Creating Partitions for RAID ###
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4. Now create sdb and sdc partitions for raid, with the help of following fdisk command. Here, I will show how to create partition on sdb drive.
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# fdisk /dev/sdb
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Follow below instructions for creating partitions.
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- Press ‘n‘ for creating new partition.
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- Then choose ‘P‘ for Primary partition.
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- Next select the partition number as 1.
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- Give the default value by just pressing two times Enter key.
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- Next press ‘P‘ to print the defined partition.
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Create Partitions
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Follow below instructions for creating Linux raid auto on partitions.
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- Press ‘L‘ to list all available types.
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- Type ‘t‘to choose the partitions.
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- Choose ‘fd‘ for Linux raid auto and press Enter to apply.
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- Then again use ‘P‘ to print the changes what we have made.
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- Use ‘w‘ to write the changes.
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Create RAID Partitions in Linux
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**Note**: Please follow same above instructions to create partition on sdc drive now.
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5. After creating partitions, verify both the drivers are correctly defined for RAID using following command.
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# mdadm --examine /dev/sd[b-c]
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# mdadm --examine /dev/sd[b-c]1
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Verify RAID Partitions
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### Step 4: Creating RAID md Devices ###
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6. Now create md device (i.e. /dev/md0) and apply raid level using below command.
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# mdadm -C /dev/md0 -l raid0 -n 2 /dev/sd[b-c]1
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# mdadm --create /dev/md0 --level=stripe --raid-devices=2 /dev/sd[b-c]1
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- -C – create
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- -l – level
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- -n – No of raid-devices
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7. Once md device has been created, now verify the status of RAID Level, Devices and Array used, with the help of following series of commands as shown.
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# cat /proc/mdstat
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Verify RAID Level
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# mdadm -E /dev/sd[b-c]1
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Verify RAID Device
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# mdadm --detail /dev/md0
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Verify RAID Array
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### Step 5: Assiging RAID Devices to Filesystem ###
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8. Create a ext4 filesystem for a RAID device /dev/md0 and mount it under /dev/raid0.
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# mkfs.ext4 /dev/md0
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Create ext4 Filesystem
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9. Once ext4 filesystem has been created for Raid device, now create a mount point directory (i.e. /mnt/raid0) and mount the device /dev/md0 under it.
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# mkdir /mnt/raid0
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# mount /dev/md0 /mnt/raid0/
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10. Next, verify that the device /dev/md0 is mounted under /mnt/raid0 directory using df command.
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# df -h
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11. Next, create a file called ‘tecmint.txt‘ under the mount point /mnt/raid0, add some content to the created file and view the content of a file and directory.
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# touch /mnt/raid0/tecmint.txt
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# echo "Hi everyone how you doing ?" > /mnt/raid0/tecmint.txt
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# cat /mnt/raid0/tecmint.txt
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# ls -l /mnt/raid0/
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Verify Mount Device
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12. Once you’ve verified mount points, it’s time to create an fstab entry in /etc/fstab file.
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# vim /etc/fstab
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Add the following entry as described. May vary according to your mount location and filesystem you using.
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/dev/md0 /mnt/raid0 ext4 deaults 0 0
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Add Device to Fstab
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13. Run mount ‘-a‘ to check if there is any error in fstab entry.
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# mount -av
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Check Errors in Fstab
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### Step 6: Saving RAID Configurations ###
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14. Finally, save the raid configuration to one of the file to keep the configurations for future use. Again we use ‘mdadm’ command with ‘-s‘ (scan) and ‘-v‘ (verbose) options as shown.
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# mdadm -E -s -v >> /etc/mdadm.conf
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# mdadm --detail --scan --verbose >> /etc/mdadm.conf
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# cat /etc/mdadm.conf
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Save RAID Configurations
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That’s it, we have seen here, how to configure RAID0 striping with raid levels by using two hard disks. In next article, we will see how to setup RAID5.
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--------------------------------------------------------------------------------
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via: http://www.tecmint.com/create-raid0-in-linux/
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作者：[Babin Lonston][a]
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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](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://www.tecmint.com/author/babinlonston/
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[1]:http://www.tecmint.com/understanding-raid-setup-in-linux/
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@ -0,0 +1,218 @@
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在 Linux 上使用 ‘mdadm’ 工具创建软件 RAID0 （条带化）在 ‘两个设备’ 上 - 第2部分
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================================================================================
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RAID 是廉价磁盘的冗余阵列，其高可用性和可靠性适用于大规模环境中，为了使数据被保护而不是被正常使用。RAID 只是磁盘的一个集合被称为逻辑卷。结合驱动器，使其成为一个阵列或称为集合（组）。
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创建 RAID 最少应使用2个磁盘被连接组成 RAID 控制器，逻辑卷或多个驱动器可以根据定义的 RAID 级别添加在一个阵列中。不使用物理硬件创建的 RAID 被称为软件 RAID。软件 RAID 一般都是不太有钱的人才使用的。
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在 Linux 中创建 RAID0
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使用 RAID 的主要目的是为了在单点故障时保存数据，如果我们使用单个磁盘来存储数据，如果它损坏了，那么就没有机会取回我们的数据了，为了防止数据丢失我们需要一个容错的方法。所以，我们可以使用多个磁盘组成 RAID 阵列。
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#### 在 RAID 0 中条带是什么 ####
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|
||||
条带是通过将数据在同一时间分割到多个磁盘上。假设我们有两个磁盘，如果我们将数据保存到逻辑卷上，它会将数据保存在两个磁盘上。使用 RAID 0 是为了获得更好的性能，但是如果驱动器中一个出现故障，我们将不能得到完整的数据。因此，使用 RAID 0 不是一种好的做法。唯一的解决办法就是安装有 RAID0 逻辑卷的操作系统来提高文件的安全性。
|
||||
|
||||
- RAID 0 性能较高。
|
||||
- 在 RAID 0 上，空间零浪费。
|
||||
- 零容错（如果硬盘中的任何一个发生故障，无法取回数据）。
|
||||
- 写和读性能得以提高。
|
||||
|
||||
#### 要求 ####
|
||||
|
||||
创建 RAID 0 允许的最小磁盘数目是2个，但你可以添加更多的磁盘，但数目应该是2，4，6，8等的两倍。如果你有一个物理 RAID 卡并且有足够的端口，你可以添加更多磁盘。
|
||||
|
||||
在这里，我们没有使用硬件 RAID，此设置只依赖于软件 RAID。如果我们有一个物理硬件 RAID 卡，我们可以从它的 UI 组件访问它。有些主板默认内建 RAID 功能，还可以使用 Ctrl + I 键访问 UI。
|
||||
|
||||
如果你是刚开始设置 RAID，请阅读我们前面的文章，我们已经介绍了一些关于 RAID 基本的概念。
|
||||
|
||||
- [Introduction to RAID and RAID Concepts][1]
|
||||
|
||||
**我的服务器设置**
|
||||
|
||||
Operating System : CentOS 6.5 Final
|
||||
IP Address : 192.168.0.225
|
||||
Two Disks : 20 GB each
|
||||
|
||||
这篇文章是9个 RAID 系列教程的第2部分，在这部分，我们将看看如何能够在 Linux 上创建和使用 RAID0(条带化),以名为 sdb 和 sdc 两个20GB的硬盘为例。
|
||||
|
||||
### 第1步：更新系统和安装管理 RAID 的 mdadm 软件 ###
|
||||
|
||||
1.在 Linux 上设置 RAID0 前，我们先更新一下系统，然后安装 ‘mdadm’ 包。mdadm 是一个小程序，这将使我们能够在Linux下配置和管理 RAID 设备。
|
||||
|
||||
# yum clean all && yum update
|
||||
# yum install mdadm -y
|
||||
|
||||
|
||||
|
||||
安装 mdadm 工具
|
||||
|
||||
### 第2步：检测并连接两个 20GB 的硬盘 ###
|
||||
|
||||
2.在创建 RAID 0 前，请务必确认两个硬盘能被检测到，使用下面的命令确认。
|
||||
|
||||
# ls -l /dev | grep sd
|
||||
|
||||
|
||||
|
||||
检查硬盘
|
||||
|
||||
3.一旦检测到新的硬盘驱动器，同时检查是否连接的驱动器已经被现有的 RAID 使用，使用下面的 ‘mdadm’ 命令来查看。
|
||||
|
||||
# mdadm --examine /dev/sd[b-c]
|
||||
|
||||
|
||||
|
||||
检查 RAID 设备
|
||||
|
||||
从上面的输出我们可以看到，没有任何 RAID 使用 sdb 和 sdc 这两个驱动器。
|
||||
|
||||
### 第3步：创建 RAID 分区 ###
|
||||
|
||||
4.现在用 sdb 和 sdc 创建 RAID 的分区，使用 fdisk 命令来创建。在这里，我将展示如何创建 sdb 驱动器上的分区。
|
||||
|
||||
# fdisk /dev/sdb
|
||||
|
||||
请按照以下说明创建分区。
|
||||
|
||||
- 按 ‘n’ 创建新的分区。
|
||||
- 然后按 ‘P’ 选择主分区。
|
||||
- 接下来选择分区号为1。
|
||||
- 只需按两次回车键选择默认值即可。
|
||||
- 然后，按 ‘P’ 来打印创建好的分区。
|
||||
|
||||
|
||||
|
||||
创建分区
|
||||
|
||||
请按照以下说明将分区创建为 Linux 的 RAID 类型。
|
||||
|
||||
- 按 ‘L’，列出所有可用的类型。
|
||||
- 按 ‘t’ 去修改分区。
|
||||
- 键入 ‘fd’ 设置为Linux 的 RAID 类型，然后按 Enter 确认。
|
||||
- 然后再次使用‘p’查看我们所做的更改。
|
||||
- 使用‘w’保存更改。
|
||||
|
||||
|
||||
|
||||
在 Linux 上创建 RAID 分区
|
||||
|
||||
**注**: 请使用上述步骤同样在 sdc 驱动器上创建分区。
|
||||
|
||||
5.创建分区后，验证这两个驱动器能使用下面的命令来正确定义 RAID。
|
||||
|
||||
# mdadm --examine /dev/sd[b-c]
|
||||
# mdadm --examine /dev/sd[b-c]1
|
||||
|
||||
|
||||
|
||||
验证 RAID 分区
|
||||
|
||||
### 第4步：创建 RAID md 设备 ###
|
||||
|
||||
6.现在使用以下命令创建 md 设备（即 /dev/md0），并选择 RAID 合适的级别。
|
||||
|
||||
# mdadm -C /dev/md0 -l raid0 -n 2 /dev/sd[b-c]1
|
||||
# mdadm --create /dev/md0 --level=stripe --raid-devices=2 /dev/sd[b-c]1
|
||||
|
||||
- -C – create
|
||||
- -l – level
|
||||
- -n – No of raid-devices
|
||||
|
||||
7.一旦 md 设备已经建立，使用如下命令可以查看 RAID 级别，设备和阵列的使用状态。
|
||||
|
||||
# cat /proc/mdstat
|
||||
|
||||
|
||||
|
||||
查看 RAID 级别
|
||||
|
||||
# mdadm -E /dev/sd[b-c]1
|
||||
|
||||
|
||||
|
||||
查看 RAID 设备
|
||||
|
||||
# mdadm --detail /dev/md0
|
||||
|
||||
|
||||
|
||||
查看 RAID 阵列
|
||||
|
||||
### 第5步：挂载 RAID 设备到文件系统 ###
|
||||
|
||||
8.将 RAID 设备 /dev/md0 创建为 ext4 文件系统并挂载到 /mnt/raid0 下。
|
||||
|
||||
# mkfs.ext4 /dev/md0
|
||||
|
||||
|
||||
|
||||
创建 ext4 文件系统
|
||||
|
||||
9. ext4 文件系统为 RAID 设备创建好后，现在创建一个挂载点（即 /mnt/raid0），并将设备 /dev/md0 挂载在它下。
|
||||
|
||||
# mkdir /mnt/raid0
|
||||
# mount /dev/md0 /mnt/raid0/
|
||||
|
||||
10.下一步，使用 df 命令验证设备 /dev/md0 是否被挂载在 /mnt/raid0 下。
|
||||
|
||||
# df -h
|
||||
|
||||
11.接下来，创建一个名为 ‘tecmint.txt’ 的文件挂载到 /mnt/raid0 下，为创建的文件添加一些内容，并查看文件和目录的内容。
|
||||
|
||||
# touch /mnt/raid0/tecmint.txt
|
||||
# echo "Hi everyone how you doing ?" > /mnt/raid0/tecmint.txt
|
||||
# cat /mnt/raid0/tecmint.txt
|
||||
# ls -l /mnt/raid0/
|
||||
|
||||
|
||||
|
||||
验证挂载的设备
|
||||
|
||||
12.一旦你验证挂载点后，同时将它添加到 /etc/fstab 文件中。
|
||||
|
||||
# vim /etc/fstab
|
||||
|
||||
添加以下条目，根据你的安装位置和使用文件系统的不同，自行做修改。
|
||||
|
||||
/dev/md0 /mnt/raid0 ext4 deaults 0 0
|
||||
|
||||
|
||||
|
||||
添加设备到 fstab 文件中
|
||||
|
||||
13.使用 mount ‘-a‘ 来检查 fstab 的条目是否有误。
|
||||
|
||||
# mount -av
|
||||
|
||||
|
||||
|
||||
检查 fstab 文件是否有误
|
||||
|
||||
### 第6步：保存 RAID 配置 ###
|
||||
|
||||
14.最后，保存 RAID 配置到一个文件中，以供将来使用。同样，我们使用 ‘mdadm’ 命令带有 ‘-s‘ (scan) 和 ‘-v‘ (verbose) 选项，如图所示。
|
||||
|
||||
# mdadm -E -s -v >> /etc/mdadm.conf
|
||||
# mdadm --detail --scan --verbose >> /etc/mdadm.conf
|
||||
# cat /etc/mdadm.conf
|
||||
|
||||
|
||||
|
||||
保存 RAID 配置
|
||||
|
||||
就这样，我们在这里看到，如何通过使用两个硬盘配置具有条带化的 RAID0 级别。在接下来的文章中，我们将看到如何设置 RAID5。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.tecmint.com/create-raid0-in-linux/
|
||||
|
||||
作者：[Babin Lonston][a]
|
||||
译者：[strugglingyouth](https://github.com/strugglingyouth)
|
||||
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](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://www.tecmint.com/author/babinlonston/
|
||||
[1]:http://www.tecmint.com/understanding-raid-setup-in-linux/
|
||||
@ -0,0 +1,146 @@
|
||||
|
||||
RAID的级别和概念的介绍 - 第1部分
|
||||
================================================================================
|
||||
RAID是廉价磁盘冗余阵列，但现在它被称为独立磁盘冗余阵列。早先一个容量很小的磁盘都是非常昂贵的，但是现在我们可以很便宜的买到一个更大的磁盘。Raid 是磁盘的一个集合，被称为逻辑卷。
|
||||
|
||||
|
||||
|
||||
|
||||
在 Linux 中理解 RAID 的设置
|
||||
|
||||
RAID包含一组或者一个集合甚至一个阵列。使用一组磁盘结合驱动器组成 RAID 阵列或 RAID 集。一个 RAID 控制器至少使用两个磁盘并且使用一个逻辑卷或者多个驱动器在一个组中。在一个磁盘组的应用中只能使用一个 RAID 级别。使用 RAID 可以提高服务器的性能。不同 RAID 的级别，性能会有所不同。它通过容错和高可用性来保存我们的数据。
|
||||
|
||||
这个系列被命名为RAID的构建共包含9个部分包括以下主题。
|
||||
|
||||
- 第1部分：RAID的级别和概念的介绍
|
||||
- 第2部分：在Linux中如何设置 RAID0（条带化）
|
||||
- 第3部分：在Linux中如何设置 RAID1（镜像化）
|
||||
- 第4部分：在Linux中如何设置 RAID5（条带化与分布式奇偶校验）
|
||||
- 第5部分：在Linux中如何设置 RAID6（条带双分布式奇偶校验）
|
||||
- 第6部分：在Linux中设置 RAID 10 或1 + 0（嵌套）
|
||||
- 第7部分：增加现有的 RAID 阵列并删除损坏的磁盘
|
||||
- 第8部分：在 RAID 中恢复（重建）损坏的驱动器
|
||||
- 第9部分：在 Linux 中管理 RAID
|
||||
|
||||
这是9系列教程的第1部分，在这里我们将介绍 RAID 的概念和 RAID 级别，这是在 Linux 中构建 RAID 需要理解的。
|
||||
|
||||
|
||||
### 软件RAID和硬件RAID ###
|
||||
|
||||
软件 RAID 的性能很低，因为其从主机资源消耗。 RAID 软件需要加载可读取数据从软件 RAID 卷中。在加载 RAID 软件前，操作系统需要得到加载 RAID 软件的引导。在软件 RAID 中无需物理硬件。零成本投资。
|
||||
|
||||
硬件 RAID 具有很高的性能。他们有专用的 RAID 控制器，采用 PCI Express卡物理内置的。它不会使用主机资源。他们有 NVRAM 缓存读取和写入。当重建时即使出现电源故障，它会使用电池电源备份存储缓存。对于大规模使用需要非常昂贵的投资。
|
||||
|
||||
硬件 RAID 卡如下所示：
|
||||
|
||||
|
||||
|
||||
硬件RAID
|
||||
|
||||
#### 精选的 RAID 概念 ####
|
||||
|
||||
- 在 RAID 重建中校验方法中丢失的内容来自从校验中保存的信息。 RAID 5，RAID 6 基于校验。
|
||||
- 条带化是随机共享数据到多个磁盘。它不会在单个磁盘中保存完整的数据。如果我们使用3个磁盘，则数据将会存在于每个磁盘上。
|
||||
- 镜像被用于 RAID 1 和 RAID 10。镜像会自动备份数据。在 RAID 1，它将保存相同的内容到其他盘上。
|
||||
- 在我们的服务器上，热备份只是一个备用驱动器，它可以自动更换发生故障的驱动器。在我们的阵列中，如果任何一个驱动器损坏，热备份驱动器会自动重建。
|
||||
- 块是 RAID 控制器每次读写数据时的最小单位，最小4KB。通过定义块大小，我们可以增加 I/O 性能。
|
||||
|
||||
RAID有不同的级别。在这里，我们仅看到在真实环境下的使用最多的 RAID 级别。
|
||||
|
||||
- RAID0 = 条带化
|
||||
- RAID1 = 镜像
|
||||
- RAID5 = 单个磁盘分布式奇偶校验
|
||||
- RAID6 = 双盘分布式奇偶校验
|
||||
- RAID10 = 镜像 + 条带。（嵌套RAID）
|
||||
|
||||
RAID 在大多数 Linux 发行版上使用 mdadm 的包管理。让我们先对每个 RAID 级别认识一下。
|
||||
|
||||
#### RAID 0（或）条带化 ####
|
||||
|
||||
条带化有很好的性能。在 RAID 0（条带化）中数据将使用共享的方式被写入到磁盘。一半的内容将是在一个磁盘上，另一半内容将被写入到其它磁盘。
|
||||
|
||||
假设我们有2个磁盘驱动器，例如，如果我们将数据“TECMINT”写到逻辑卷中，“T”将被保存在第一盘中，“E”将保存在第二盘，'C'将被保存在第一盘，“M”将保存在第二盘，它会一直继续此循环过程。
|
||||
|
||||
在这种情况下，如果驱动器中的任何一个发生故障，我们将丢失所有的数据，因为一个盘中只有一半的数据，不能用于重建。不过，当比较写入速度和性能时，RAID0 是非常好的。创建 RAID 0（条带化）至少需要2个磁盘。如果你的数据是非常宝贵的，那么不要使用此 RAID 级别。
|
||||
|
||||
- 高性能。
|
||||
- 在 RAID0 上零容量损失。
|
||||
- 零容错。
|
||||
- 写和读有很高的性能。
|
||||
|
||||
#### RAID1（或）镜像化 ####
|
||||
|
||||
镜像也有不错的性能。镜像可以备份我们的数据。假设我们有两组2TB的硬盘驱动器，我们总共有4TB，但在镜像中，驱动器在 RAID 控制器的后面形成一个逻辑驱动器，我们只能看到逻辑驱动器有2TB。
|
||||
|
||||
当我们保存数据时，它将同时写入2TB驱动器中。创建 RAID 1 （镜像化）最少需要两个驱动器。如果发生磁盘故障，我们可以恢复 RAID 通过更换一个新的磁盘。如果在 RAID 1 中任何一个磁盘发生故障，我们可以从另一个磁盘中获取相同的数据，因为其他的磁盘中也有相同的数据。所以是零数据丢失。
|
||||
|
||||
- 良好的性能。
|
||||
- 空间的一半将在总容量丢失。
|
||||
- 完全容错。
|
||||
- 重建会更快。
|
||||
- 写性能将是缓慢的。
|
||||
- 读将会很好。
|
||||
- 被操作系统和数据库使用的规模很小。
|
||||
|
||||
#### RAID 5（或）分布式奇偶校验 ####
|
||||
|
||||
RAID 5 多用于企业的水平。 RAID 5 的工作通过分布式奇偶校验的方法。奇偶校验信息将被用于重建数据。它需要留下的正常驱动器上的信息去重建。驱动器故障时，这会保护我们的数据。
|
||||
|
||||
假设我们有4个驱动器，如果一个驱动器发生故障而后我们更换发生故障的驱动器后，我们可以从奇偶校验中重建数据到更换的驱动器上。奇偶校验信息存储在所有的4个驱动器上，如果我们有4个 1TB 的驱动器。奇偶校验信息将被存储在每个驱动器的256G中而其它768GB是用户自己使用的。单个驱动器故障后，RAID 5 依旧正常工作，如果驱动器损坏个数超过1个会导致数据的丢失。
|
||||
|
||||
- 性能卓越
|
||||
- 读速度将非常好。
|
||||
- 如果我们不使用硬件 RAID 控制器，写速度是缓慢的。
|
||||
- 从所有驱动器的奇偶校验信息中重建。
|
||||
- 完全容错。
|
||||
- 1个磁盘空间将用于奇偶校验。
|
||||
- 可以被用在文件服务器，Web服务器，非常重要的备份中。
|
||||
|
||||
#### RAID 6 两个分布式奇偶校验磁盘 ####
|
||||
|
||||
RAID 6 和 RAID 5 相似但它有两个分布式奇偶校验。大多用在大量的阵列中。我们最少需要4个驱动器，即使有2个驱动器发生故障，我们依然可以重建数据，同时更换新的驱动器。
|
||||
|
||||
它比 RAID 5 非常慢，因为它将数据同时写到4个驱动器上。当我们使用硬件 RAID 控制器时速度将被平均。如果我们有6个的1TB驱动器，4个驱动器将用于数据保存，2个驱动器将用于校验。
|
||||
|
||||
- 性能不佳。
|
||||
- 读的性能很好。
|
||||
- 如果我们不使用硬件 RAID 控制器写的性能会很差。
|
||||
- 从2奇偶校验驱动器上重建。
|
||||
- 完全容错。
|
||||
- 2个磁盘空间将用于奇偶校验。
|
||||
- 可用于大型阵列。
|
||||
- 在备份和视频流中大规模使用。
|
||||
|
||||
#### RAID 10（或）镜像+条带 ####
|
||||
|
||||
RAID 10 可以被称为1 + 0或0 +1。它将做镜像+条带两个工作。在 RAID 10 中首先做镜像然后做条带。在 RAID 01 上首先做条带，然后做镜像。RAID 10 比 01 好。
|
||||
|
||||
假设，我们有4个驱动器。当我写了一些数据到逻辑卷上，它会使用镜像和条带将数据保存到4个驱动器上。
|
||||
|
||||
如果我在 RAID 10 上写入数据“TECMINT”，数据将使用如下形式保存。首先将“T”同时写入两个磁盘，“E”也将同时写入两个磁盘，这一步将所有数据都写入。这使数据得到备份。
|
||||
|
||||
同时它将使用 RAID 0 方式写入数据，遵循将“T”写入第一个盘，“E”写入第二个盘。再次将“C”写入第一个盘，“M”到第二个盘。
|
||||
|
||||
- 良好的读写性能。
|
||||
- 空间的一半将在总容量丢失。
|
||||
- 容错。
|
||||
- 从备份数据中快速重建。
|
||||
- 它的高性能和高可用性常被用于数据库的存储中。
|
||||
|
||||
### 结论 ###
|
||||
|
||||
在这篇文章中，我们已经看到了什么是 RAID 和在实际环境大多采用 RAID 的哪个级别。希望你已经学会了上面所写的。对于 RAID 的构建必须了解有关 RAID 的基本知识。以上内容对于你了解 RAID 基本满足。
|
||||
|
||||
在接下来的文章中，我将介绍如何设置和使用各种级别创建 RAID，增加 RAID 组（阵列）和驱动器故障排除等。
|
||||
|
||||
--------------------------------------------------------------------------------
|
||||
|
||||
via: http://www.tecmint.com/understanding-raid-setup-in-linux/
|
||||
|
||||
作者：[Babin Lonston][a]
|
||||
译者：[strugglingyouth](https://github.com/strugglingyouth)
|
||||
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](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]:http://www.tecmint.com/author/babinlonston/
|
||||
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