RAID is the short form of Redundant Array of Independent Disks. RAID refers to the way of combining different independent and small disks into single storage of large size. The disks which constitute this array are called the array members. In order to get upgraded speed and performance, several physical disks are integrated as one set. Different levels of RAID types: RAID 0, RAID 1, RAID 5, RAID 6 and RAID 10.
Different levels of RAID processing
It is the initial level of the process. In a RAID 0 system data is written to disks in the array as different blocks. Performance can be enhanced by using several disks at once. There are different controllers, one controller per disk, which is used to increase performance. RAID 0 can be used to combine two drives storage into a single volume. RAID 0 is supported on Linux, OS X, and Windows. The benefit of RAID 0 is that one disk failure does not affect the data of the second disk.
In this data is stored in two drives one is data reader and the other one is a mirror drive. In case of failure of one drive the other drive is used for data recovery and operated. We need a minimum of 2 drives for RAID 1 array.
This is based on the combination of RAID 0 and RAID 1. This level inherits RAID 0 performance and RAID 1 fault tolerance.
This can survive failure of 1 member disk or many numbers of non-adjacent disks. It uses both striping and mirroring techniques to store data in an array. There are 3 subtypes of the 1E layout.
It is the regular level of RAID process. In RAID 5 we need minimum 3 disks which can work for 16 blocks. The disks are divided into data blocks and every disk has an equal part of the data block written. The data is dispersed over all drives of raid backup server instead of writing on a single drive. The computer can determine the data from another block of the set in case of data unavailability. Which means that RAID 5 array supports single disk failure without any data loss. In RAID 5 a hardware controller is suggested even it is identified in software. To increase the performance of writing, the extra cache can be used.
This is one of the RAID 5 variations. In additional to RAID 5, RAID 5E have integrated share space to rebuild the array in case of one member disks fails. The advantage of RAID 5E compared to RAID 5 is high read and write space with the dedicated drive. However, this leads to the complexity of rebuild during member disk failure. This can be created by using a standalone controller like the IBM ServeRAID controller.
Recovery of array parameters in RAID 5E is similar to RAID 5.
RAID 6 is equal to RAID 5 but the same data is written on two disks. This means to support 2 disks we need 4 disks. If the 2 disks are lost another 2 can be used. Unlike the RAID 5 in RAID 6, the array can survive on the second failure. In RAID 5 one disk fails, replacing with a new one takes time, during this if another disk fails data may be lost forever.
The benefits of RAID 0 and RAID 1 can be grouped to a single system. The mirroring of all data on secondary disks while using each disk set can speed up data transfers and also provides security.
Several mirrors are created where the data is arranged in tapes on multiple disks, later extracted disk sets are mirrored. RAID 10 level has fault tolerance which is equal to RAID 1 with advancing read or write speeds on a single RAID 1 volume. In this RAID 10 level, 4 disks are needed.
For any business, data is the key resource. Data loss may result in business loss. Keep the regular back up to save some effort to access or to protect in case of drive failures. Using raid backup server along with storage configurations can be an economical way to secure and access the data.
Characteristics of RAID
RAID storage techniques
Following are the main techniques of storing data in a raid storage system:
All the existing RAID types are based on either of these three techniques and also a combination of the above.
RAID can be created in the following ways:
This is the most inexpensive solution. This method uses operating system drivers. Most of the operating systems have an in-built capability to create many RAID levels. For example, the Windows operating system allows the user to create RAID 0, RAID 1 and RAID 5. However, it is inseparably linked with the Windows operating system and so its partitions cannot be used like in dual boot.
Software RAID is created based on the user computer and so this uses host CPU for implementation. In case of RAID 0 and 1, the load on the CPU is negligible whereas, in case of RAID types that are based on parity, 1 to 5 percent of CPU load is used depending on the number of disks. However, for practical purposes this is negligible.
It must be remembered that there are some limitations to boot the system if software RAID is used. Only RAID 1 support boot partition, and it is impossible to system boot with software RAID 0 and 5. In most cases, software RAID does not implement hot swapping and so is not suitable where continuous availability is required.
Hardware RAID is formed by using separate hardware. This can be done in one of the following ways:
Advantages of Hardware RAID over Software RAID
RAID 5 Recovery
The manual process to recover RAID 5 is too complex and time-consuming if you are not an expert. Using ReclaiMe Free Raid Recovery you can recover drive much easily.
If you want to recover data manually, you have to determine the parity position and rotation to get the full configuration of your array. This is because like RAID 0, RAID 5 is a redundant array and stores parity data.
RAID 0 Recovery
RAID 0 can fail due to any of the following reasons:
Member disk failure
As RAID 0 arrays are non-redundant, so if one of the disks on the raid storage system fails, data is lost forever. However, you can try to recover data from other member disks. Only the files having a size smaller than (N-1) *(block size) can be recovered. If the file was stored on the failed disk, data cannot be recovered even if the file size is less than the above-mentioned threshold.
Various other factors can also lead to RAID 0 failures. For example, operator error, controller error or RAID 0 controlling software. In these cases, the configuration metadata is lost, but member disks are working fine. With these failures, it is possible to recover data from RAID 0. Firstly, you determine the raid backup server configuration.
You can either opt for manual or software process for RAID 0 recovery. The software process is similar to the RAID 5 recovery process using the software described above.
For manual recovery, you need to determine raid storage devices order manually. You can use log files with a timestamp for this purpose. Also, you need a disk viewer tool. Whenever a fragment of the suitable file is found on one of the member disks, this tool tracks which disk contains the next fragment and so on.
To determine the first disk, you can again use the disk viewer tool. Search the member disks for:
For a hardware RAID 0, the block size can be determined by looking up possible values or checking in the manual which block can be used in your RAID 0 implementation. For software RAID 0, The standard value can be used. For example, Windows use 128 sector block for RAID 0.
On a hardware RAID 0, data mostly starts at the start of the hard drive. This is equivalent to setting start offset of member disk to 0. For a software RAID, the offsets are mostly identical. This can be identified by locating the volume sector.
Hot Swapping hard drive when RAID crashes
If there is no raid backup server downtime when RAID crashes and you need to change the raid backup drives, then below is the process to swap hard drive when RAID crashes.
RAID 5 disk mirroring provides highly secure data protection in the event of failure. To create a RAID 5 array, you need 3 disks of similar capacity. RAID creates an exact copy on each of the raid backup drives and protects data in case of any of the drive failure. The usable capacity in RAID 5 is the disk size of the smallest drive. This is useful for personal and business purposes.
When the RAID operates in functional mode, the status is shown as Ready in ‘Storage Pools’.
In the event of a drive failure, you can check the drive status by the following steps:
To install a new drive to rebuild RAID 5, follow these steps:
The new disk volume information is shown in System logs.
Using RAID as a backup
RAID array can be used as a raid backup server with backup software. If you have a Mac Pro with some external drives connected to it, you can connect RAID array by Thunderbolt or USB 3. You can change the configuration of backup software so that it copies data to RAID array.
Raid backup server offers extra protection for your backup over what you would have on a single drive. If any of the drives fails, device software will warn you and you can swap raid backup drives and this will ensure that your backups are reliable every time. This will prevent any occurrence of unreadable backup when your computer drive fails. However, using RAID alone as a backup might not be a good idea. Below are some of the problems you might encounter by using RAID as a backup alone:
To have all the drives in a single unit powered by the same electric supply and controller cannot be safe at all. In case of a power surge, all the disks might get damaged. But this does not mean that you should not use RAID, just back it up properly.