Why RAID 5 is very useful ?

Explain Raid 5 (Striping with distributed parity)

1. Thus, all read and write operations can be overlapped. RAID-5 stores parity information but not redundant data (but parity information can be used to reconstruct data). RAID-5 requires at least three and usually five disks for the array. It's best for multi-user systems in which performance is not critical or which do few write operations.

2. ---

   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. Similar to level 3, but may provide higher performance if most I/O is random and in small chunks. Database servers are an example.Block Interleaved Distributed Parity:
3. Following are the key points to remember for RAID level 5.

---

• Minimum 3 disks.
• Good performance ( as blocks are striped ).
• Good redundancy ( distributed parity ).
• Best cost effective option providing both performance and redundancy. Use this for DB that is heavily read oriented. Write operations will be slow.

Diagram

[ Read More ]

Technical Definition of RAID 50

Explain Raid 5+0 (50) (Striping of RAID 5 logical drives)

1. RAID 50 is a combination of two basic RAID techniques. It combines striping (RAID 0) with independent data disks with distributed parity (RAID 5). It stripes data across at least two RAID 5 arrays. The easy way to think of RAID 50 is as RAID 5 with an extra pair of suspenders. RAID 50 offers increased write performance and better data protection, including faster rebuilds, than RAID 5 in the event of a disk failure. While performance degrades in the event of a disk failure, it doesn't degrade as much as it would in a RAID 5 array because a single failure only affects one of the arrays, leaving the other fully functional. In fact, RAID 50 can sustain up to four drive failures if each failed disk is in a different RAID 5 array.

   ---

2. RAID 50 is best used for applications that need high reliability, and that need to handle high request rates and high data transfer with lower cost of disks than a RAID-10. This type consists of a series of RAID-5 groups and striped in RAID-0 fashion to improve RAID-5 performance without reducing data protection.
3. RAID 0+5 or RAID 50 is a combination of RAID levels that utilizes multiple RAID 5 sets striped in a single array. In a RAID 0+5 array, a single hard drive failure can occur in each of the RAID 5 sides without any loss of data on the entire array. If, however more than one disk is lost in any of the RAID 5 arrays all the data in the array is lost. As the number of hard drives increase in an array, so does the possibility of a single hard drive failure. Although there is an increased write performance in RAID 0+5, once a hard drive fails and reconstruction takes place, there is a noticeable decrease in performance, data/program access will be slower, and transfer speeds on the array will be effected.

Diagram

[ Read More ]

How to explain RAID?

What is technical Definition of RAID ?

• RAID (redundant array of independent disks; originally redundant array of inexpensive disks) is a way of storing the same data in different places (thus, redundantly) on multiple hard disks. By placing data on multiple disks, I/O (input/output) operations can overlap in a balanced way, improving performance. Since multiple disks increases the mean time between failures , storing data redundantly also increases fault tolerance.
• Redundant array of independent disks (RAID) is a storage technology used to improve the processing capability of storage systems. This technology is designed to provide reliability in disk array systems and to take advantage of the performance gains offered by an array of multiple disks over single-disk storage.
• Raid is a method of connecting multiple drives into one logical storage unit raid partition used id ‘fd’

---

What is Concept of RAID?

RAID's two primary underlying concepts are:

• Distributing data over multiple hard drives improves performance.
• Using multiple drives properly allows for any one drive to fail without loss of data and without system downtime.

[ Read More ]

How to explain RAID 10 ?

Explain Raid 1+0 (Mirroring and striping)

1. RAID 0+1 or RAID 10 is a combination of RAID Levels that utilizes multiple RAID1 (mirrored) sets into a single array. Data is striped across all mirrored sets. As a comparison to RAID 5 where lower cost and fault tolerance is important, RAID 0+1 utilizes several drives to stripe data (increased performance) and then makes a copy of the striped drives to provide redundancy. Any disk can fail and no data is lost as long as the mirror of that disk is still operational. The mirrored disks eliminate the overhead and delay of parity. This level array offers high data transfer advantages of striped arrays and increased data accessibility (reads). System performance during a drive rebuild is also better than that of parity based arrays, since data does not need to be regenerated from parity information, but is copied from the other mirrored drive.
2. Combining RAID-0 and RAID-1 is often referred to as RAID-10, which offers higher performance than RAID-1 but at much higher cost. There are two subtypes: In RAID-0+1, data is organized as stripes across multiple disks, and then the striped disk sets are mirrored. In RAID-1+0, the data is mirrored and the mirrors are striped.
3. A RAID subsystem that increases safety by writing the same data on two drives (mirroring), while increasing speed by interleaving data across two or more mirrored "virtual" drives (striping). RAID 10 provides the most security and speed.

---

Diagram

[ Read More ]

How to explain RAID 0 ?

Explain RAID 0 Levels with diagram

1. A RAID 0 (also known as a stripe set or striped volume) splits data evenly across two or more disks (striped) with no parity information for redundancy. RAID 0 was not one of the original RAID levels and provides no data redundancy. RAID 0 is normally used to increase performance, although it can also be used as a way to create a small number of large logical disks out of a large number of small physical ones. A RAID 0 can be created with disks of differing sizes, but the storage space added to the array by each disk is limited to the size of the smallest disk. For example, if a 120 GB disk is striped together with a 100 GB disk, the size of the array will be 200 GB.
2. Raid 0 is not redundant. In level 0 data Is split across drives, resulting in higher data throughputs. Since no redundant information is stored, performance is very good, but the failure of any disk in the array result is data loss. This level is commonly referred to as striping.
3. Striping – writes data across multiple drives. Involves partitioning each drive storage space into stripes that can vary in size from 2KB to 1MB. These stripes are interleaved in a repeated sequential manner.

---

Diagram

[ Read More ]

Raid 1

Technical Definition of RAID 1

1. Raid level 1 provides redundancy by writing all data to two are more drives. The performance of level 1 array tends to be faster on reads and slower on writes compared to a single drive but if other drives fails no data is lost. This is good entry level redundant system, since only two drives are regained ; however, since one drive is used to store a duplicate of the data, the cost per megabyte is high. This level is commonly referred to as mirroring.
2. Disk mirroring, also known as RAID 1, is the replication of data to two or more disks. Disk mirroring is a good choice for applications that require high performance and high availability such as transactional applications, email, and operating systems. Because both disks are operational, data can be read from them simultaneously, which makes read operations quite fast. Write operations, however, are slower because every write operation is done twice.
3. This type is also known as disk mirroring and consists of at least two drives that duplicate the storage of data. There is no striping. Read performance is improved since either disk can be read at the same time. Write performance is the same as for single disk storage. RAID-1 provides the best performance and the best fault-tolerance in a multi-user system.

---

Diagram

[ Read More ]