RAID array failed and a disk dropped out: should I rebuild?
Every attempt you make can turn recoverable data into data that can no longer be recovered.
If a disk has dropped out of your RAID array and the array is still running, the data needs to be backed up first. A rebuild puts strain on the other disks and a second failure can lead to data loss. If the array will not open at all or more than one disk has dropped out, do not start a rebuild; mark the disks without changing their order and contact us.
- If the array is running, first back up the important data to another disk.
- Write down which disk dropped out and the warnings on the screen.
- If you are going to remove the disks, mark their bay order.
- Record the controller model and the RAID type.
- Do not start a rebuild when more than one disk has dropped out.
- Do not remove the disks and swap their positions.
- Do not choose 'create new array' or 'initialize' on the controller.
- Do not delete the controller configuration or reset the controller.
- Do not try one of the disks on a different controller.
What happens depending on the RAID type?
| RAID type | How many lost disks can it keep running with? | What to watch out for |
|---|---|---|
| RAID 0 | None; if one disk goes, all the data is affected | The array cannot continue with a single disk |
| RAID 1 | One disk (mirroring) | Back up the remaining healthy disk as well |
| RAID 5 | One disk | There is a risk of a second disk failing during the rebuild |
| RAID 6 | Two disks | If more than two disks are lost, the array fails |
| RAID 10 | One disk from each mirrored pair | If both disks in the same pair go, the data is affected |
Why is a rebuild risky?
During a rebuild, all the disks in the array are read from start to finish. Disks manufactured around the same time and run for the same length of time show similar wear. If one has dropped out, the others have probably weakened as well. A rebuild increases this load, and if a second disk fails in RAID 5, the array goes down. That is why you need to back up first and, if possible, start the rebuild only after that.
RAID is not a backup
RAID provides resilience against disk failure. It does not protect against deleted files, ransomware, fire or controller errors. So even if you use RAID, you should have a separate backup. For the same situation on NAS devices, see our NAS page.
What is done in the lab?
The condition of each disk is examined separately. Where necessary, disks with physical faults are handled in a Class 100 (ISO 5) clean environment. The disks are then put together in their original order, the structure of the array is determined and the data is transferred to a healthy disk. The method depends on the fault.
How long does it take and how much does it cost?
Standard jobs take 10 business days on average, urgent jobs 24 business hours on average. The actual time depends on the type of fault, sourcing the parts needed and the capacity of the disk. Some jobs are completed within a few hours, while others can take months.
The price depends on the type of fault, the parts needed and the time the work takes. After the analysis we send you the exact price in writing. If you do not accept the quote, you get your device back without paying. Not every case falls within the free analysis scope. For requests outside the free analysis scope, you receive written information about the analysis fee before any work begins. For details, see what determines the price and how long it takes.
Can the data always be recovered?
No. If more than one disk is physically damaged, if the array has been recreated or its configuration deleted, or if the disks have been overwritten, some or all of the data may not be recoverable. We cannot know the outcome without carrying out an analysis. After the analysis, you will be informed about the situation.
Frequently asked questions
If two disks drop out of RAID 5, is the data lost?
The array will not work, but the data cannot always be considered lost. If the damage to one of the disks is limited or logical, recovery may be possible. We determine this through analysis.
Why do two disks drop out within days of each other?
Disks bought in the same period and carrying the same load wear in a similar way. The heavy reading during a rebuild can also trigger a weak disk to drop out.
What should I do if the RAID controller fails?
The disks may be intact. The structure of the array is stored on the controller, so talk to us before fitting a new controller or touching any array creation options.
Do I pay anything if I don't accept the quote?
No. If you do not accept the quote after the analysis, you get your device back without paying. In cases where it cannot be foreseen at which stage the data will become reachable, the price may be set after the data has been recovered, based on the time and resources spent on the work. In that case you are under no obligation to pay. Not every case falls within the free analysis scope. For requests outside the free analysis scope, you receive written information about the analysis fee before any work begins.
Why isn't free analysis available in every case?
For some requests a short assessment of the device is enough, and we can offer a free analysis. For other requests, our specialists can only reach an opinion or a result after spending many hours working on your device with professional tools. Because what we call the analysis stage involves carrying out the technical work that has to be done, we may not be able to offer those hours free of charge.
What do you do during the analysis?
During the analysis we actually start the professional technical work that needs to be done. Many businesses, on the other hand, say they offer a 'free analysis' to attract customers and get the device brought to them; once the device has been handed over, without spending any time on it, they say something like 'we will work on it; if it works it costs this much, if not, that much'. Having got customers to hand over their devices with the words 'free analysis', and since the customer will want the work to continue rather than go to the trouble of taking the device back, they put in no effort or time, which is how they can claim to offer a 'free analysis' in every case. In reality this is little more than a trap to attract customers.
Do you charge a service fee?
We do not charge anything under the name of a service fee. We do offer free analysis. For requests outside the free analysis scope, the analysis fee is communicated in writing at the start. Some businesses advertise with phrases like "600 TL data recovery service fee", leading customers to believe they will get their data recovered for 600 TL. That is how they attract customers. We do not work in such an unethical way.
Let's assess your situation together: call 0212 909 56 19 or write to us on WhatsApp. See our contact page for the address and opening hours.
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