RAID 5 rebuild and data recovery

Rebuilding A Failed Raid  Server System.

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  RAID  Emergency Technical Support Team.

A RAID is a method of using a number of discrete hard disk drives or solid state drives in a data storage unit that presents users a more efficient and robust (less prone to downtime) means of access to their data. The term RAID is an acronym  for  Redundant Array of Independent Devices.  An Array being a number of  virtually interconnected hard drives, usually hard disk drives , with a practical upper limit determined by application, performance and capacity. There are a number of commonly used  Array types and you can find technical detail concerning the popular RAID 5 configuration by clicking through to my RAID 5 data recovery page.

A  RAID 5 System is designed to tolerate a single hard disk drive failure,  rebuild its data structures and continue to operate satisfactorily, however coincident disk failures will result in operational failure. Mathematically if a single independent element has  a probability of failure of 1/10000 then two elements  will have a dual probability of failure  1/100,000,000. However when a  supplier creates an interdependent array of identical elements,  the probability of  a complete array failure will be median figure.   Regardless of the mathematics concerning mean time between failures or MTBF, hard drive elements in a RAID Array have a shared  environmental aspect  that also contributes to a risk  of failure. Power surge, power outage,  data deletion, ransomware and malware attacks, rebuild errors, and poor maintenance practice, the list is long.  Incorrect removal and replacement of hard drive  elements is a common mistake that adversely affects the integrity of a RAID 5 configured  system  and the service it provides.

Is a RAID-5 server operation reliable?

In a RAID 5 configuration, data is striped across single hard disk drive elements and an error detection algorithm  (single-parity) is used. RAID 5 reliability is dependent on all drives within the array operating correctly in order to fully auto rebuild  in the event of a single point of failure. Despite the deployment of helium filled hard disk drives and other enterprise class construction technology,  hard drives of a  higher capacity are always more susceptible to increasing numbers of bad sectors, error rates and failure. “Putting  all your apples in one basket is never a good idea”. You can find a good explanation of how RAID 5 is constructed here

Rebuilding your failed RAID 5 configured server.

When a RAID 5 configured system fails, it is essential that you firstly attempt to gracefully power it down and that you do not attempt  to replace hard disk drives or force a hard disk drive back online. This  can result in incorrect data being written to the volume and cause irreparable data loss.

Create write protected duplicates of  all healthy hard drives.

We create copies of the original hard drives using write-blocking technology that preserves the original data and we note the order in which the drives are configured  in the array.

Rebuild  and repair faulty hard disk drives and produce “as good as” copies.

The failed RAID 5 systems we receive generally have two or more faulty non working hard drives that have dropped out of the array and caused the failure of the system and the service it provides.  The first task is therefore to undertake Hard Drive repairs and then attempt to make  write protected copies that can be used to reconstruct and eventually rebuild of the system.

RAID 5 metadata determines which drive can be excluded from a rebuild.

Each hard drive in a RAID array has metadata that describes its function within the array. The metadata describes the last time that data was written to a given drive and this helps to determine which hard drive/s have exhibited as faulty.  If two hard drives have failed we only need one of  these failed drives data in order to facilitate a rebuild of the system and its  data volume/s.

RAID 5 uses special parity functions to reconstruct any data on a single failed hard drive element however it cannot reconstruct its data if two hard drives have failed.  After one hard drive fails, the rest of the array functions normally. But as time passes, the data on the furloughed  hard drive becomes increasingly out-of-date. Sometimes, two or more hard drives fail almost instantaneously

We use the metadata to determine  drive order, parity, rotation, stripe size.

The parity data created is  written across all hard drives in the array. In order to reconstruct the failed array.  Using the metadata on each drive, our RAID recovery team will determine how the data in the array has been distributed striped across the drives.

Emulate the physical RAID 5 array and find the logical units on the array.

Our RAID recovery technicians string the disk images together and then identify how the RAID 5 config  storage has been logically allocated. They then locate the file system within the logical elements that will point to your stored data and facilitate an extraction.The file-system comprises a  RAID system’s logical structure, acting as a road map to point you to the locations of your files.

We Run a scan on the RAID 5 array.

Logical corruption of a RAID 5 file system will affect the value of the recovery to our client.  We scan the volume/s and  detect any files that are orphaned  as a result of a damaged or corrupt  file system.  Once complete we produce a file listing for our clients to check through and determine the usefulness  of the available data.

We extract all available data from the failed RAID 5 array.

Our RAID Team will transfer all  a clients data on to new external drives and return it to you

More about Datlabs RAID recovery services during lock down