An Overview of RAID Levels. Part -I

By | August 24, 2011

RAID is an important feature of Web Hosting Services which is provided as main feature with Dedicated Server Hosting services. and it comes with various levels, a web hosting client can choose it as per his requirements.

  • RAID-0: This RAID technique has striping but lack of data redundancy and that’s why it can only provide the good performance without fault-tolerance.
  • RAID-1: This is based on Disk mirroring and includes minimum two drives which duplicates the data stored. Without any striping read performance is improved. It provides best performances for multiple users with fault-tolerance feature.
  • RAID-2: Striping exists here across multiple disks with error checking and correcting (ECC) information.
  • RAID-3: One drive is used for striping and storing parity information. Error checking and correcting (ECC) information features is used for detection errors. After calculating the exclusive OR (XOR) of data stored on the other driver, data recovery can be achieved. The drawback with RAID-3 is it can not overlap I/O because I/O operations address all drive at the same time. RAID-3 is recommended for single user systems which have long record applications.
  • RAID-4: It is targeted towards the large stripes, so that webmasters can read records from any single drive, which provides the benefit of overlapped I/O for reading operations only, for write operations no I/O overlapping advantage because all writing operations need to update the parity drive.
  • RAID-5: This level of RAID is based on rotation of parity array. Drawback of no write operation with overlapped I/O in RAID-4 is removed in this level. Unlike RAID-4 both read and write operations can be overlapped with RAID-5. It stores parity information but lacks data redundancy, despite this absence of data redundancy its possible to reconstruct data by using parity information. Minimum three disks are required for array in RAID-5. For the multi-user systems which perform less critical and limited write operations, RAID-5 is recommended.

Still there are many levels of RAID which will be shared in next post.