Redundant Array of Independent Disks (RAID) may be a technology that uses multiple smaller disks simultaneously, which function as one large volume. It provides a specific method of accessing one or many separate hard disks, thereby decreasing the risk of losing all data if at all a hard disk fails or is susceptible to damages, and it also helps in improving access time.
The RAID technology helps users to:
- Maintain a large amount of knowledge storage.
- Achieve a greater level of input/output performance.
- Achieve greater reliability through data redundancy.
The basic idea of the RAID storage system is to group multiple small and cheap hard disks into an array of hard disks that gives performance greater than that of single large hard disk. A RAID storage system may be a collection of hard disks that employment as and also appear to be one large capacity disk drive to the user. the most advantage of the RAID storage system is that if any disk within the RAID array fails or is vulnerable to damage; the system still continues to function with none loss of knowledge . this is often possible because the info of every separate hard disk is stored on another disk in an array.
The RAID system allows multiple simultaneous accesses to different files on different hard disks, which reduces the time required to seek out the info on a hard disk. Data transfer considerably increases on a RAID system over one hard disk.
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Levels of RAID Storage System
1. RAID Level 0
– Disk Striping
It is the only RAID level, which doesn’t involve any redundancy and fragments the file into user-defined stripe size of the array. Then it sends these stripes to each disk within the array. As RAID 0 doesn’t have redundancy, it allows this RAID level to supply the simplest overall performance characteristics of the only RAID levels.
Following are the features of RAID level 0: Disk Striping
- Split data into blocks and writes equally across multiple hard drives
- If any drive fails, data recovery isn’t possible
- It doesn’t provide data redundancy
- It requires a minimum of two drives to line up
- The main advantage of this level is its high level of input/output performance, because it spreads the inputs/outputs across multiple channels and hard drives
- Data transfer rate is fast and most effective
– Disk Mirroring
RAID 1 generally executes mirroring because it duplicates or copies the drive data on to 2 different drives employing a hardware RAID controller or a software. If one among the drives fail, the opposite will function as one drive until a user replaces the failed drive with a replacement one.
Following are the features of disk mirroring:
- Writes multiple copies of knowledge to multiple drives at an equivalent time
- It provides data redundancy by completely duplicating the drive data to multiple drives
- If one drive fails, data recovery is feasible
- It requires a minimum of two drives to line up
- The performance of this level is quicker on reading data and slower on writing data compared to the only disk drive because the info is distributed between multiple hard drives
- This level provides the simplest protection of knowledge
- The main disadvantage of this level is that data access speed is slow
- It provides high data consistency and continued data availability just in case of failure of any hard disk drive
- It gives 100% data redundancy and doesn’t require rebuild time
2. RAID 2
RAID 2 is that the only level among all the RAID levels that doesn’t implement even one among the quality techniques of parity, mirroring or striping. It uses a way almost like striping with parity. It includes splitting of knowledge at the bit level and distributing it to numerous data disks and redundancy disks.
Hamming codes, which may be a sort of error correcting code (ECC), help to calculate these redundant bits. When a user writes something to an array, the system calculates the codes and writes them along side the info to dedicated ECC disks.
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3. RAID 3
RAID 3 uses byte-level stripping with a fanatical parity disk, which stores checksums. It also supports a special processor for parity codes calculation. This RAID cannot cater multiple data requests simultaneously. If a failure occurs, it enables data recovery by an applicable calculation of the parity bytes, and therefore the remaining bytes which relate with them.
4. RAID 5
Uses byte level data striping across multiple drives, and distributes the parity information among all member drives. Data writing process is slow. It requires a minimum of three drives to line up. The RAID stripes and distributes the error detection and correction code or Data and parity code across three or more drives.
5. RAID 10
RAID 10, also referred to as RAID 1+0, may be a combination of RAID 0 (Striping Volume Data) and RAID 1 (Disk Mirroring) to guard data. It requires a minimum of four drives to implement. it’s same fault tolerance as RAID level 1 and therefore the same overheads as mirroring alone. It allows mirroring of disks in pairs for redundancy and improved performance, then stripes data across multiple disks for max performance. The user retrieves data from the MID if one disk in each mirrored pair is working; however, if two disks within the same mirrored pair fail, the info isn’t available.
Host Protected Areas (HPA) and Device Configuration Overlays (DCO)
Hard disk drives and other storage media can have hidden areas like Host Protected Areas (HPA) and Device Configuration Overlays (DCO).
- Host Protected Areas (HPA): First introduced within the ATA-4 standard, HPA may be a reserved area on a tough disc drive (HDD) or a Solid State Drive (SSD) that’s not visible to the OS . This space stores data, which the users, BIOS or OS of a system cannot modify, change, or access it. It can store information about HDD utilities, diagnostic tools, boot sector code, etc.
The three ATA commands which will help users to make and use a hidden protected area are:
- IDENTIFY DEVICE
- SET MAX ADDRESS
- READ NATIVE MAX ADDRESS
- Device Configuration Overlays (DCO): First introduced within the ATA-6 standard, DCO is a further hidden area available on modern hard disks, which enables system vendors to shop for HDDs of varying sizes from different manufactures and configure all of them to possess equal number of sectors. DCO refers to the world hidden from the system, BIOS, and users. It can help the users to enable/disable features on the HDD. to work out the particular size and features of a disk, it’s required to use the command the DEVICE_CONFIGURATION_IDENTIFY.
These areas can convince be tricky to the users as perpetrators can hide data in them without knowledge of the investigators. The intruders use certain tools to switch and write to the HPA and DCO areas on the HDD. Investigators can use tools like EnCase, TAFT (an ABTA (IDE) forensics tool), Sleuth Kit, etc. to detect and image HPA and/or DCO areas.
Questions related to this topic
- What is the best RAID for 4 drives?
- What are the different types of RAID levels?
- What is Redundant Array of Inexpensive Disk how it has improved reliability and performance?
- What is the most common RAID level?
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