Replacing a hard drive in a RAID system is a delicate operation, during which your data is particularly vulnerable. If the deployment of RAID reinforces the security and / or the performance of your IS, it should not therefore exempt from the implementation of solid data backup or recovery procedures.

RAID system failures: understanding and anticipating

 

Performing a RAID failure simulation, when installing a new system, can be useful for your business. This will allow you to understand the configuration of your RAID system, to test the correct implementation of the administrative and hardware procedures in the event of a failure and, if necessary, to trigger a suitable PCA / PRA.

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The most frequently used RAID systems are RAID 0, RAID 1, RAID 5 and RAID 6. Their relationships between performance, fault tolerance and data security depend on the way the hard drive arrays that make up them are aggregated. With the exception of RAID 0, which is only dedicated to read / write speed, any RAID system involves the security of at least one hard drive.


The security of a RAID is nevertheless quite relative, including on systems considered to be reliable. The majority of failures begin with the loss of a single hard drive in the configuration. But a cascade effect can occur when the disks in a cluster or a RAID belong to the same series or to the same batch: having had the same activity, they can become inoperative in a very short time.

Disk Drive Close Up

Replacing a RAID hard drive: the different steps

 

Replacing a hard drive in a RAID system involves several steps.

During most failures, an alert is sent to the RAID administrator (email alert, audible signal, indicator light, etc.). It is therefore important to raise these alerts, to initiate a doubt and to launch the appropriate procedures. As long as the RAID storage volume is accessible and before any other operation, it is essential to make a data backup and / or to check the daily backups.

The second step is to replace the failed hard drive. This is the most critical step in fault management: with the exception of RAID 6, the system is no longer secure at this time. Since the delivery of a replacement disk can sometimes take several days, the vulnerability period can be very long.

Hard Drive Disc Close Up 4

The third step is to initiate the reconstruction of the data on the RAID system following the replacement of the defective hard drive. An equally critical and delicate phase, this process involves irreversible writing operations, both on the new hard disk and sometimes on the parity zones of other disks.

Cascade failures on RAID system: your last resort

 

As we mentioned above, RAID system failures can happen when the hard drives are from the same batch or the same series. These cascading failures can then lead to the loss or inaccessibility of your data. Data recovery operations on a RAID system should then be considered.

During the second step (and always with the exception of RAID 6), it is important not to replace more than one defective hard drive at the risk of permanently losing your data. And in the event of data loss, the best action will be to turn off the hard drive power.

If a hard drive in the RAID system becomes inoperative during the data reconstruction phase, bad information may be written irretrievably on the other drives. These corrupted entries can then lead to a permanent loss of data.

In all cases, it is therefore preferable to contact a data recovery laboratory, which can extract your data and make a copy of your defective hard disks before any other operation (disk replacement, reconstruction operation of the data, etc.).

 

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