What are RAID Servers?

[Lafaso870]

What are RAID Servers or systems and why should a customer opt for it? How a RAID system can be beneficial? How a data is backed-up on a server using an off-site backup solutions ? Also, what are the advantages of backing the data off-site?

[crystal]

Raid server and Raid systems are similar to each other as per my knowledge. The main advantage or you can say the feature of a RAID drive is that it increases the performance and reliability of the system. The RAID drive are one of the convincing example that could be used in a web server.

[Rachael]

RAID stands for redundant array of independent disks. A RAID server provides with increased storage facilities and also increased reliability through redundancy. This is mainly done with the combination of the disk drive components. The data is distributed among the drives in various ways and the data distribution is determined in terms of RAID levels.

[John233]

If you are running linux software RAID you should not try to mount partitions like that. You need to mount raid devices.
You do not need to use rescue mode to rebuild software RAID. Its just 5 minute job.

[Jeffrey]

RAID 0 (block-level striping without parity or mirroring) has no (or zero) redundancy. It provides improved performance and additional storage but no fault tolerance. Hence simple stripe sets are normally referred to as RAID 0.

In RAID 1 (mirroring without parity or striping), data is written identically to multiple disks (a "mirrored set"). Although many implementations create sets of 2 disks, sets may contain 3 or more disks.

In RAID 2 (bit-level striping with dedicated Hamming-code parity), all disk spindle rotation is synchronized, and data is striped such that each sequential bit is on a different disk. Hamming-code parity is calculated across corresponding bits on disks and stored on one or more parity disks. Extremely high data transfer rates are possible.

In RAID 3 (byte-level striping with dedicated parity), all disk spindle rotation is synchronized, and data is striped such that each sequential byte is on a different disk.

RAID 4 (block-level striping with dedicated parity) is identical to RAID 5 (see below), but confines all parity data to a single disk, which can create a performance bottleneck.

RAID 5 (block-level striping with distributed parity) distributes parity along with the data and requires all drives but one to be present to operate; drive failure requires replacement, but the array is not destroyed by a single drive failure.

RAID 6 (block-level striping with double distributed parity) provides fault tolerance from two drive failures; array continues to operate with up to two failed drives. This makes larger RAID groups more practical, especially for high-availability systems.

[aimiez]

RAID stands for Redundant Array of Inexpensive Disks It was a system developed whereby a large number of low cost hard drives could be linked together to form a single large capacity storage device that offered superior performance, storage capacity and reliability over older storage solutions. It has been widely used and deployed method for storage in the enterprise and server markets, but over the past 5 years has become much more common in end user systems.

There are three primary reasons that RAID was implemented:
1. Redundancy
2. Increased Performance
3. Lower Costs

[jessica30]

RAID is short for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers but aren't generally necessary for personal computers. RAID allows you to store the same data redundantly (in multiple paces) in a balanced ay to improve overall performance.

There are number of different RAID levels:
Level 0 -- Striped Disk Array without Fault Tolerance: Provides data striping (spreading out blocks of each file across multiple disk drives) but no redundancy. This improves performance but does not deliver fault tolerance. If one drive fails then all data in the array is lost.
Level 1 -- Mirroring and Duplexing: Provides disk mirroring. Level 1 provides twice the read transaction rate of single disks and the same write transaction rate as single disks.
Level 2 -- Error-Correcting Coding: Not a typical implementation and rarely used, Level 2 stripes data at the bit level rather than the block level.
Level 3 -- Bit-Interleaved Parity: Provides byte-level striping with a dedicated parity disk. Level 3, which cannot service simultaneous multiple requests, also is rarely used.
Level 4 -- Dedicated Parity Drive: A commonly used implementation of RAID, Level 4 provides block-level striping (like Level 0) with a parity disk. If a data disk fails, the parity data is used to create a replacement disk. A disadvantage to Level 4 is that the parity disk can create write bottlenecks.
Level 5 -- Block Interleaved Distributed Parity: Provides data striping at the byte level and also stripe error correction information. This results in excellent performance and good fault tolerance. Level 5 is one of the most popular implementations of RAID.
Level 6 -- Independent Data Disks with Double Parity: Provides block-level striping with parity data distributed across all disks.
Level 0+1 -- A Mirror of Stripes: Not one of the original RAID levels, two RAID 0 stripes are created, and a RAID 1 mirror is created over them. Used for both replicating and sharing data among disks.
Level 10 -- A Stripe of Mirrors: Not one of the original RAID levels, multiple RAID 1 mirrors are created, and a RAID 0 stripe is created over these.
Level 7: A trademark of Storage Computer Corporation that adds caching to Levels 3 or 4.
RAID S: (also called Parity RAID) EMC Corporation's proprietary striped parity RAID system used in its Symmetrix storage systems.

[Kailey]

Logical RAID data recovery uses the raw images of all the server's media by examining the low-level data sectors. Technicians must determine both the exact layout of volumes which span or are striped across multiple drives and what fixes to filesystem structures are needed to get access to the important data.

[Sushant]

RAID server means schemes that can divide and replicate data among multiple hard disk drives.