What To Expect With a RAID Server & Data Recovery

 


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What To Expect With a RAID Server & Data Recovery

Common RAID Server Failures And Data Loss Issues

  • RAID controller failure or configuration changed
  • Two or more hard drives fail or go offline
  • Server crashes and won't remount the array or volume(s)
  • Configuration becomes corrupt or damaged
  • Adding incompatible hard drives
  • Hardware conflicts
  • Software corruption
  • Virus infection, software and operating system upgrades
Recovering Data From RAID 0 Hard Drive Configurations

Because data on a RAID array or volume is typically critical to business continuity, when it becomes inaccessible due to one or more hard drives failing, a bad RAID controller, multiple hard drive failure, failed upgrade or damaged striping, RAID status in degraded mode, or errors with the MFT mount points, it is imperative that you shut the server down and get help.

Permanent data loss often occurs when hard drives are swapped, moved from one position to another or placed in other machines in an attempt to rebuild or repair the array. Formatting a boot drive or partition can also damage or remove striping, which reduces the recoverability of data and causes permanent loss.

RAID 0 Configurations

RAID Level 0 requires a minimum of 2 hard drives to implement. A RAID 0 configuration is a striped array without fault tolerance. A benefit to this RAID configuration is that it reduces the hard drives used. If any hard disk fails, the entire volume will be lost completely. For this reason, a RAID 0 configuration should never be used for any server which contains sensitive information, such as a SQL server or Exchange server.

RAID 1 Configurations

RAID Level 1 requires a minimum of 2 drives to implement. For the best performance, the controller must be able to perform two concurrent separate reads per mirrored pair or two duplicate writes per mirrored pair. In certain instances a RAID 1 array can recover from multiple and simultaneous hard drive failure, it also uses the simplest storage design. The overhead is very high at 100%, so RAID 1 may not be ideal for a larger server.

RAID 1+0 Configurations

RAID Level 10 (1+0) requires a minimum of 4 drives to implement. A RAID 10 is a striped array with segments consisting of RAID 1 arrays and having the same fault tolerance as RAID level 1 plus the overhead fault-tolerance of mirroring. In certain instances a RAID 10 array can recover from multiple and simultaneous hard drive failure. Because of limited scalability and high inherent costs, RAID 1+0 is typically used in database server applications like an Exchange Server or SQL database server which requires high performance and high fault tolerance levels.

RAID 0+1 Configurations

RAID Level 0+1 (0+1) requires a minimum of 4 drives to implement. A RAID 0+1 is a striped array with segments consisting of RAID 0+1 arrays and having the same fault tolerance as RAID level 0+1 plus the overhead fault-tolerance of mirroring. In certain instances a RAID 0+1 array can recover from multiple and simultaneous hard drive failure, however, a single drive failure will cause it to run as RAID 0. Because of limited scalability and high inherent costs, RAID 0+1 is typically used in imaging applications general file servers. It tends to be a high performance solution with reduced emphasis on reliability.

RAID 2 Configurations

RAID Level 2 requires a minimum of 2 drives to implement. Each bit of data word is written to a data disk drive (4 in this example: 0 to 3). Each data word has its Hamming Code ECC word recorded on the ECC disks. On read, the ECC code verifies correct data or corrects single disk errors. In certain instances a RAID 2 array can recover from multiple and simultaneous hard drive failure. The entry level costs for RAID 2 are extremely high, making it not commercially viable. RAID 2 performs ‘on the fly’ error corrections.

RAID 3 Configurations

RAID Level 3 requires a minimum of 3 drives to implement. RAID 3 is highly efficient and single disk failure affects performance only slightly. The data block is subdivided ("striped") and written on the data disks. Stripe parity is generated on writes, recorded on the parity disk and checked on reads. In certain instances a RAID 3 array can recover from multiple and simultaneous hard drive failure. It is commonly used for applications with very high throughput, such as video production, live streaming, and video editing. Read and write speed is high.

RAID 4 Configurations

RAID Level 4 requires a minimum of 3 drives to implement. Each entire block is written onto a data disk. Parity for same rank blocks is generated on writes, recorded on the parity disk and checked on reads. In certain instances a RAID 4 array can recover from multiple and simultaneous hard drive failure. It has the worst write rate of RAID designs, and has a very complex controller setup, however it reads rapidly and is highly efficient.

RAID 5 Configurations

RAID Level 5 requires a minimum of 3 drives to implement. It is the most versatile array design, and is used for databases, mail servers, file servers, etc. A RAID 5 is a striped array with segments consisting of RAID 5 arrays and has the highest data reading speed of RAID models. Each entire data block is written on a data disk; parity for blocks in the same rank is generated on writes, recorded in a distributed location and checked on reads. In certain instances a RAID 5 array can recover from multiple and simultaneous hard drive failure.

RAID 5+0 Configurations

RAID Level 5+0 requires a minimum of 5 drives to implement. It is highly expensive to implement and due to the required synchronization of the spindles has limited disks that can be used. A RAID 5+0 is a striped array with segments consisting of RAID 3 arrays and has fairly high data transfer rates. In certain instances a RAID 5+0 array can recover from multiple and simultaneous hard drive failure.

Jason Perry

ADR Data Recovery can rebuild failed RAID arrays, repair damaged RAID volumes, recover hard drive data, and restore critical data your company needs if you call before the damage is too severe. Once platters are damaged, striping overwritten or changed completely, the chances of getting your data back are slim.

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