The volume repair tool can cause further damages in the logical volume and results in unrecoverable data loss. In this case, also, the corruption in logical volume triggers the Admin to use volume repair tool to run and repair logical drives. The Operating System in the rebuild may not be able to read the sections in the metadata, which leads to logical corruption thus making the data unusable. The data-size is practically split into half thus damaging RAID configuration. For example, a new configuration is forced with 32K stripe size which was initially set up as 64K size. If the RAID Array loses its configuration and the user tries to rebuild it using an incorrect configuration, then it leads to data damage. The result is unusable data and ultimately unrecoverable system. If one of the disks used to rebuild RAID array is a degraded drive and the other is a new drive, then, after the rebuild, this combination overwrites the good parity with the bad one. Instead of repairing, these utilities may sometime cause even more damage leading to metadata deletion and irrecoverable RAID Array.

Since there is logical volume corruption, and the parity build is also not possible, it is imperative to run volume repair tools like CHKDSK, FSCK and similar. All these disks as mentioned are affected and ultimately damaged. Moreover, the data in Data disk B1 is also affected, thus creating Logical volume corruption. During RAID Rebuild, if this data is overwritten with new Parity, then the Parity on Disk 3 in Stripe 1 is treated as Data Disk and not Parity, and that creates corruption in ‘Logical Volume’. In Raid 5 Array, data was initially available on C1 of Disk 2 available on Stripe 1.

An ideal RAID 5 Array is shown below for illustration: Here the drives are not in proper order, and Parity rebuild on these Drives may lead to overwriting the important user’s data. When the Parity is overwritten, it is difficult to recreate damaged or missing HDD.Īnother example is ‘disordered RAID Array’ during RAID Rebuild. Further, the zeroed disk will prevent the Drive Rebuild. Here the Rebuild RAID has destroyed the original Parity. In a RAID Rebuild configuration, the parity is updated with a zeroed disk instead of HDD rebuild.

The original and rebuild differ in configurations – Parity and Data are overwritten.

Stripe sizes are not similar – Parity and Data are overwritten.

One of the Drives is missing – Parity and Data are overwritten.

If there is misconfiguration related to Rebuild RAID, as in the following cases:

Drives out of order (both are overwritten – Data and Parity).

Degraded drive (forced online with overwritten Parity).

If there is misconfiguration related to Rebuild Parity, as in the following cases: If either of these is faulty, the Array will not work appropriately. When a RAID Administrator rebuilds RAID, then the most probable elements to reassemble it correctly are classified into Parity and Array configurations. Rebuilds are based upon two factors – Parity and Array. Hence the above causes and the Recovery methods/ solutions are associated with RAID 5 Configurations and Rebuild. Note: Here we have taken RAID 5 as an example. To avoid an incorrect rebuild of RAID Array, it is essential to know the exact causes which may lead to data loss. The higher the configuration of capacity drives, the higher the latency period and hence data-inaccessibility for an extended time that may stretch to for long hours. This is a common case with higher configurations of the RAID. Sometimes, after rebuilding the entire RAID Array, it is discovered that the RAID is not perfectly built.

Monitoring the vital stats of the disk drive in a RAID Array can help Administrators or users to decide if any disk needs replacement, thus sidestepping irreversible data losses. It is possible to avoid latency by monitoring the disks proactively with dedicated Disk monitors. The only problem with rebuilding RAID is that during the ‘Rebuild RAID Array’ process, the performance is negatively affected due to latency. The most logical way to reassemble data on a failed Disk Array is ‘copy the data to a spare drive’ and replace the failed one, followed by using the RAID Algorithms and parity data to reassemble data to a new drive.

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