RAID Rebuild - Everything You Need To Know

RAID rebuild guide on how to prevent data lose, cut time on rebuild, problems to avoid with RAID rebuild and more. A RAID rebuild guide for beginners!

By Linda J
By Linda J
Last Modified February 26, 2020

One of the biggest hurdles you’ll face in your quest to keep your storage array running flawlessly is avoiding data loss during the dreaded rebuild process. Here are a few tips from the certified RAID recovery experts at TTR Data Recovery.

What is RAID Rebuild?

Raid Rebuilds

RAID rebuild is a data reconstruction process that puts every data into its proper order and places when an HDD (Hard Disk Drive) needs replacing. 

The intelligence of RAID algorithms and parity data comes into place when an unexpected hard drive failure has occurred. These two capacities of RAID makes it possible to reassemble the data that was funneled on a spare drive by the RAID array. 

These amazing capacities quickly activate in the event of an unexpected disk failure to save the crucial data that RAID is tasked to protect. It maintains its accurate operation even with sophisticated data reassembling. 

RAID Basics

RAID arrays use groups of linked physical hard drives to create redundant architectures that can survive the failure of individual elements. Although you see a single logical device when you access your RAID’s storage from a command prompt or GUI interface, they actually incorporate complex arrangements that leverage techniques like parity, striping, mirroring and other data storage methods to provide superior performance and dependable redundancy.

In the world of storage devices, RAID arrays hold a place of honor thanks to their versatility, reliability and accessibility. Although these configurations are extremely commonplace, however, they come with unique data recovery challenges.

What You're Up Against

Raid Rebuild What You're Up Against

One of the advantages of RAID arrays is that you can recover their contents following many kinds of failures. If you lose some of the disks in your volume, then you might be able to use the information on the remaining devices to reconstruct the lost data. This process is known as rebuilding.

The big problem with rebuilding is that the operation doesn’t always go smoothly. For instance, some rebuilds require you to wait for days until the process completes. Even worse, you might come up against a range of hurdles, such as unrecoverable read errors.

Every RAID administrator’s greatest nightmare is losing data during a rebuild. When you don’t follow the recommended procedures correctly, you could end up permanently eliminating vital information or corrupt the records that would normally let you access lost data.

Make a mistake, and you might lose any hope you had of completing a data recovery operation on your own.

Improve Your Odds With These Pointers

Fortunately, you can do more than just cross your fingers in the hopes that your RAID rebuilds will magically go according to plan. The following tips are great ways to lower the risk of mid-rebuild losses.

Steer Clear Of Known Hazards

Raid Rebuilds Hazard

Certain factors significantly heighten the chances that you’ll lose data during a rebuild. For instance, if you’re trying to rebuild parity, then you face greater loss dangers by working with drives that include overwritten, or zeroed, parity records.

Other high-risk endeavors include reconstructing degraded drives that you’ve forced online even though their parity was overwritten or out-of-ordered devices whose parity and data were both overwritten.

Parity rebuilds aren’t the only tasks that you should approach carefully. Don’t try to rebuild a RAID array when a drive has gone missing, bears a dissimilar configuration or uses a disparate striping scheme. Without accessible parity records, you’re running the risk of attempting to reconstruct data that it’s impossible to recover via normal means.

Suppose you try to correct parity by performing a rebuild on a drive, but the devices are out of order. Your good intentions might lead to other information getting erased via overwriting.

Understand Your RAID Level

RAID systems aren’t all equivalent. The different numeric levels that designate what kind of array you’re using are more than just naming schemes: They represent widely dissimilar data storage and redundancy record keeping techniques.

It’s critical that you know the ins and outs of your array’s configuration before diving into a RAID recovery. Since a significant percentage of storage devices fail at some point in their service lifetimes, you should pick architectures that meet your needs and reduce your risks.

You also have to understand the nuances of what you’ve chosen so that you can rebuild properly.

Know Whether Rebuilding Is Even an Option

Unlike professional hard drive recovery, RAID rebuilds can be extremely risky. While a secure data recovery service can use forensic techniques and specialized diagnostic tools to extract data from a drive, RAID rebuilds are primarily software-driven, self-guided processes.

If you attempt to do more than your RAID level can support, such as trying to rebuild an entire array from fewer surviving disks than the minimum number required to recover information, then you’re probably going to end up losing some information forever.

Make Backups Before and During RAID Rebuilds

Rebuilding is designed to be a procedure of near-last resort, so you shouldn’t rely on it to solve all of your problems. If you’re smart, then you’ll create a regular system task that backs up your RAID array periodically so that you don’t lose too much if it fails.

You should also back up all of the disks in the RAID array before attempting a rebuild. Ensure that you label each backup clearly so that you can maintain the proper order if you need to reconstruct the volume from these reserves.

How Does Raid Rebuilds Impact End Users?

Raid Impacts On User

RAID Rebuild is a process for data reconstruction. This
process takes place when there is a need to replace an (HDD) Hard Disk Drive.

RAID rebuilds provide convenience for users by recreating data on arrays of RAID in case of an unexpected multiple disk failure.

This kind of solution is crucial for businesses that are sensitive to any disks failures. For enterprises that hold and process essential information, RAID rebuilds help them to recover from significant disks failures and resume their operations.

This technology enables businesses to save precious time by fixing their disk failures as fast as possible. Because with a problem like this that can halt the operations of a business, RAPID rebuild is a crucial solution to return a company’ service as soon as possible.

For businesses that hold sensitive information about their clients or customers, RAPID rebuild helps to protect this data by reconstructing this information after a disk failure scenario.

Reconstruction here means putting all these data on their
original and proper order. This technology would not be in any way useful for businesses if it can merely reconstruct. It responds to the business’ needs to recover the affected data on its original order. This capability has protected a lot of companies from significant financial losses and possible lawsuits.

With RAPID rebuilds capabilities, it can prevent problems from blowing up into proportions by operating fast and minimize the impacts of these failures. With this, it can return everything from normal operations.

How Does Raid Rebuilds Impact End Users?

Raid Rebuild Times

Raid rebuild times has been a problem for many users because of the rapid advancements in catechnology, especially on the capacities of hard drives. The larger the hard drives’ size gets, the slower the RAID rebuild time can be.

With drives that are now on the 4, 6, 8 and even 10 Terabytes capacities, problems with RAID rebuild times has become more and more of a problem.

But fortunately, there are tried and tested solutions to
manage this problem even with the inevitable advances of technology that inflates the rebuild times problem.

To solve this particular RAID problem is not to halt the
progress of technology, but to utilize the solutions that lie underneath the existing technologies that we are using.

One solution to cope up with this problem is to give the
recovery process a higher priority than the input/output (I/O) in the array of RAID.

Another solution is for the host to retrieve the maximum amount of data possible before a RAID recovery is initiated by allowing a failed drive to assist it.

Erasure coding is another solution to manage this problem because through this erasure; it can reduce the disk data to rebuild time and utilize less capacity overhead.

Estimated Time for RAID Rebuild

Estimated Time Raid Rebuild

The estimated reconstruction time depends on the capacity of
the drive, its types, and its (rpm) or revolutions per minute. For a 300 GB hard drive, it takes 1 hour, 450 GB, 1.5 hours, 600 GB, 1.8 hours; all the said hard drives have a Fiber Channel types of hard
drives and 15,000 revolutions per second.

For SAS type hard drives with 15,000 revolutions per second, the estimated reconstruction time for a 300 GB hard drive is 1 hour, 450 GB, 1.5 hours, and for 600 GB, 1.8 hours.

For SAS type hard drives with only 10,000 revolutions per
second, the estimated reconstruction time for a 450 GB hard drive is 2.5 hours, and 600 GB for 3.8 hours.

Lastly, for SATA type drives with 7,200 revolutions per
second, the estimated reconstruction for a 2TB hard drive is 12.8 hours while a 3TB hard drive is 18.3 hours.

How To Rebuild Raid Arrays Without Losing Data

RAID/Server Data Recovery

Exact Causes That Lead To Data Loss

There are three common causes of data loss that is related to rebuild operations. Users must take not of these things as it can help them to prevent any data loss while they are in a rebuild RAID array operation.

  • Physical nature
    Since the raid system is composed of physical materials such as hard drives, it will always be prone to physical damages like wear and tear and drive head damages.
  • Accidental deletion of data
    Accidentally deletion of data because of a human error would result in data loss but users can quickly recover it if the data is unwritten.
  • Failure of RAID controller
    Since RAID controller manages all the hard drives in the RAID system, any failure in the controller would result in inaccessible hard drives, including the data within it. It can stem from power surges and rebooting the RAID can result in overwritten data that cannot be retrieved.

Rebuild Errors That Can Lead To Data Loss

Gaithersburg Data Loss

Errors in this kind of operations can be avoided, only if users are well aware of the common mistakes that they should avoid to prevent data loss. Here are the most common errors that users should know about: 

  • Rebuilding Using An Incorrect Configuration
    If a user applied an incorrect configuration in a hope to rebuild a RAID array, it would undoubtedly lead to a damaged data. An example of this is when a new configuration is forced in a smaller stripe size which was initially set up on a larger scale. With this, the data-size will split and will be damaging the RAID configuration.
  • O.S Cannot Read Sections In The Metadata
    Data corruption can stem from the operating system. If it cannot read the sections in metadata when it is in a rebuild mode, then logical corruption may occur. Users must be aware that Operating Systems has this kind of limitation. This knowledge is crucial when diagnosing a problem related to a RAID system.

Misconfigurations Related To Rebuild Parity

Misconfigurations must be avoided in rebuild parity to ensure a smooth operation in one’s system. Avoiding these things will ensure that one’s system can run in a desired manner.

Here are the misconfigurations that you need to avoid.

  • Misconfiguration # 1 Zeroed drive (overwritten Parity).
  • Misconfiguration # 2 Degraded drive (forced online with overwritten Parity)
  • Misconfiguration # 3 Drives out of order (Overwritten Data and Parity)
  • Misconfiguration # 4 Drive cables have improper connection and shield.
  • Misconfiguration # 5 Cables that are being used to connect the multiple disks to the controller are incorrect.
  • Misconfiguration # 6 The Small Computer System Interface or (SCSI) terminators may have come loose.
  • Misconfiguration # 7 SCSI devices have improper physical connections.
  • Misconfiguration # 8 SCSI cables that are shorting out, cut, not fully attached to the connector on end or exposed can produce data transfer problems.
  • Misconfiguration # 9 SCSI cable has improper connections to the drive and the controller card. Errors can also stem from the misaligned pins on the SCSI and the pins on the devices.
  • Misconfiguration # 10 Users are not using the right SCSI cable.

Misconfigurations Regarding Rebuild Raid

  • Misconfiguration # 1 Stripe sizes are not similar (Overwritten Parity and Data).
  • Misconfiguration # 2 One of the Drives is missing (Overwritten Parity and Data)
  • Misconfiguration # 3 The original and rebuild differ in configurations (Overwritten Parity and Data)

Disordered Arrays

Disordered Arrays is the term used when the drives are in an improper order. Many might see this as a ‘minor issue’ in the overall RAID system. But with the complicated set up within this system, even minors issues can cause significant problems.

There is a need to be very careful when rebuilding the RAID system, because minor misalignments can produce negative impacts on the whole system.

Users should always remember that parity rebuild on these
misaligned drives may lead to the overwriting of essential and confidential data. The overwritten data, users must know, are unretrievable.

Users must be aware if misalignments are occurring on their system, to avoid any operations that may work with these errors that can produce more significant problems.

Misalignment is a cause for concern, and it can turn into an
unmanageable problem if it is allowed to “work in harmony” with another error.

New Configurations of RAID 5

RAID 5 can use disk striping with parity. These two configurations are perfect combinations that ensure data protection from any failures.

It sets the standard by evenly balances read and writes, a method that is now widely used in most RAID methods today. RAID 5 has one of the most secured configurations of all RAID because of the vast extent of its parity data on all drives.

It can continuously check if the data that it holds have been overwritten to prevent the possibility that these essential data can turn into unretrievable files.

No wonder why it is the most trusted of all RAIDS because of
its tight-knit approach on securing data.

How To Rebuild Raid Array Without Data Loss

Raid Data Loss

Never Create New Files On A Disarrayed Disk

Creating new files can result in overwritten data and can
turn it into unretrievable files. Users must always remember not to run critical applications or, more importantly, create any new files on the disarrayed disk because this will surely corrupt the drive. A corrupted drive can directly affect all other areas, so it is necessary to avoid this failure at all cost.

After recovery, you may do all these prohibited actions.

  • Image The Raid Before Rebuilding
    The main advantage of imaging the RAID before a rebuild is it provides total protection for your data. Even without a guarantee from the rebuild, it will shield the data and imaging program can layout forensic or sector/block disk-image.
  • Separate Volumes
    One of the first things that users need to do, before everything else, is to have a back-up of their data. This measure ensures that users can have recoverable data in case of any failure.

    Also, it ensures that their data can still be retrieved even in the case of actively overwritten files. Remember that overwritten data can turn into an unretrievable file and will be inaccessible.
  • Test Backup With Multiple Restores
    There is a need for users to image each drive separately. This action will ensure that a useful restore can jumpstart. Remember that it must be done, before and not after starting the rebuilding process.

    This action will not produce its desired result if users are not able to initiate this action before the process.
  • Run CHKDSK or FSCK tool only after taking the backup
    Before running any repair utilities, users must make sure to initiate a secured and reliable back up and confirm it with proper steps in restoring. It will make the file system consistent through the option of overwriting file pointers.

    Having a consistent file system ensures that everything can run smoothly, data are neatly organized and are in proper order.
  • Do not add, move, or delete files
    There are specific actions that can complicate and slow the recovery process of data.

    Any delays in the recovery process can surely have a direct impact on the operations of any business. This problem is an unwanted operations scenario, so users should avoid adding, deleting, or moving data if their RAID system is severely affected by failures, misalignments, and other related problems.

Don’t Let Failures Catch You

Data losses occur at the oddest of times, but this shouldn’t stop you from being as prepared as possible. Tracking the health and performance statuses of your RAID array drives on a regular basis makes it much easier to anticipate when things might go south.

If you’re consistently aware of how your hardware is doing, then you can replace faulty equipment promptly before it causes other problems that make rebuilds harder.

Finally, never hesitate to call a professional. If you don’t know the exact cause of a failure, then it’s far better to solicit expert assistance than to try rebuilding since you could make the situation even worse.

Learn more about maintaining your data security and privacy without potentially sacrificing your RAID’s integrity. Chat with TTR Data Recovery today.