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In both businesses and households, NAS devices are a popular solution thanks to the wide selection of devices and hard drives, where most buyers can find what suits them best — whether the main criterion is price, high capacity or expected reliability. In addition to the NAS and drives, it is worth considering potential power outages and investing in a UPS (uninterruptible power supply). For optimal integration, check the manufacturer's website for a NAS and UPS combination that can communicate with each other — allowing the UPS to safely shut down the NAS when battery capacity runs low.
RAID Repair after a Drive Failure
If a NAS is configured with a RAID variant that tolerates the failure of one or more drives, it is essential to replace the failed drive with a new one immediately. We have encountered many cases where the client — or even their IT administrator — ignored the warning signs. The data was still accessible at that point and everything appeared to work normally. For example, RAID 1 or RAID 5 can tolerate the failure of a single drive. Drives in a NAS are typically purchased at the same time and are the same model, likely from the same production batch. This means that due to a manufacturing defect, multiple drives may fail in quick succession. What could have been a simple single-drive replacement can then turn into a complex data recovery from the array. Do not ignore warning signs from your NAS.
Data Recovery from RAID
A RAID array can fail due to simultaneous failure of multiple drives, a malfunction of the NAS itself, a file system error, an external event the user did not anticipate, or an incorrect intervention by the operator. The probability of such a scenario is of course far lower than if you entrust valuable data to a single ordinary drive. However, it can happen, and in such a case the user should avoid any attempts that could make the situation worse. Contact us for a free consultation.
RAID data recovery is typically complex, and it is not advisable to work directly with drives that contain valuable data. Some of them may be defective. The first step is to create a binary copy of all drives in the array. This process can be demanding — technologically (especially if one or more drives have failed), in terms of time, and in terms of storage capacity. For example, if we have a RAID array of 4 × 6 TB drives, we will need 24 TB of free space for the binary copies. Only then can we proceed — in read-only mode or with write simulation to a separate layer — to perform the operations necessary to reassemble the RAID and recover the data. But do you know all the array parameters, and do you have the necessary experience and equipment?
If the fault lies solely with the NAS and all drives are healthy, it may in some cases be possible to restore the array using a new NAS of the same brand. However, the manufacturer bears no responsibility for any errors. The responsibility always lies with the user.
The aim here is not to provide a how-to guide for recovering data from RAID, but to highlight the importance of following the correct procedure when a RAID array or NAS fails. Detailed information about failure types, indicative pricing and our recovery process can be found on the RAID Data Recovery page. If you have a specific question, we are happy to help.
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Hard Drives (HDD) Suitable for NAS
A NAS typically contains multiple hard drives that need to be capable of running 24/7. It is therefore essential to use drives that the manufacturer has designed for this type of use. Factors such as higher vibration levels, different operating temperatures, and expected longer operating hours compared to a regular desktop computer must be taken into account. NAS-rated drives have a more robust construction, a longer expected lifespan and are simply suitable for this purpose.
Whether to use the same brand and identical model or a combination of different brands is perhaps a topic for a longer discussion. The drives should definitely have the same parameters, all must be rated for NAS operation, and under no circumstances should you mix drives with conventional recording (CMR) and shingled recording (SMR). We wrote about the differences between CMR and SMR drives in our article SMR — the hidden feature of some WD, Seagate and Toshiba drives. Should you worry about it?. In general, it is probably better to use drives with conventional recording (CMR) in a NAS.
Which drives to use in a NAS? The major manufacturers offer Western Digital RED or GOLD, Seagate IronWolf or EXOS, and Toshiba N300. Even among these, the choice depends on the type of use, expected lifespan, etc. If you need help choosing, do not hesitate to contact us.
Choosing the Right RAID Configuration. Fault Tolerance and Performance
There are many possible RAID configurations. Beyond the basic distinction between RAID 0, 1, 5, 6, 10, 01 and others, additional parameters need to be set. Modern NAS devices largely handle this automatically, so for the purposes of this article we will assume that users who wish to configure advanced parameters already have sufficient experience and know what they are doing.
In the vast majority of cases, NAS users will want the array to tolerate the failure of at least one drive. For a small two-bay NAS, the most common configuration will be RAID 1 — mirroring two drives, where each drive contains identical data. For NAS devices with more bays, RAID 5 is a likely choice — it requires at least 3 drives and tolerates the failure of one. RAID 6 is similar but can tolerate the failure of up to 2 drives and requires a minimum of 4 drives. For example, Synology NAS devices also offer SHR — Synology Hybrid RAID, an automated RAID management system. It has its advantages and disadvantages, but if you are a beginner and do not want to spend too much time on RAID configuration, SHR is a good choice.
UPS — A Sensible Investment
A NAS is essentially a small computer, and especially when it uses traditional hard drives (HDD), a power outage is never good for a running NAS. All drives shut down unexpectedly, which can lead to data loss or, in worse cases, a drive failure or the collapse of the entire array. It pays to invest a little extra in a UPS (uninterruptible power supply). There is a wide range of affordable and premium UPS models on the market. Ideally, choose a UPS recommended by the manufacturer of your NAS. The NAS should be able to communicate with the UPS via a USB cable and instruct it to shut down safely when the battery capacity is running low.
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Monitoring NAS and Drive Health
Hard drives can start developing errors or fail entirely over time. The NAS itself also requires occasional maintenance — cleaning, firmware updates and general checks. It is a good practice to configure the NAS to send reports when an error is detected. This allows you to identify a failing drive early and replace it promptly. A visual check of the NAS can also help — in the event of a failing drive, the NAS will typically alert you with LED indicators and an audible alarm. Logging into the NAS admin interface is another way to check for errors or unusual conditions.
Updating the NAS operating system can bring new features, fix issues from previous versions and patch security vulnerabilities. These are the expected benefits. However, sometimes an update may not be thoroughly tested and polished. Unless there is a critical security vulnerability that makes the update essential, it is wise to wait a while before installing it and read other users' experiences online.
Both RAID and the NAS Itself Can Fail
RAID is not a backup — a fact that many people mistakenly believe otherwise. If your RAID fails or your NAS breaks down and you have no backup, you will learn this the hardest way possible. Data recovery is usually possible, but the outcome heavily depends on the user following the correct procedure. More about the correct procedure and recovery options can be found on the NAS Data Recovery or RAID Data Recovery page.
Jean-Marie Dufrasne contributed to this article. Thank you.
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- By Frantisek Fridrich
- Parent Category: Blog
- Explanations and Tips
