A NAS that becomes unavailable at once can be very alarming since this is typically the location for shared files, important backups etc. And “not accessible” could be anything from a brief network glitch to the death of one disk or even the complete failure of the RAID array. What is safe to do next depends upon why. Here’s how to determine what went wrong and then recover your data should the NAS itself fail.
There are many different reasons why you may not be able to connect to your NAS. Perhaps the NAS is perfectly good but there is something amiss with the network. Perhaps there was a failure of one of the disks. Possibly the RAID array has dropped. Before doing anything, find out which; making incorrect decisions about what recovery steps to take can result in losing all of your data.
Essentially, a NAS is a miniature personal computer running its own operating system with its own network connection, and a group of disks combined together into a RAID array. There are three areas that could create a problem with accessing the NAS: either with the network (altered IP address, DNS/router problems, faulty cable, permission problems), in which case the data remains entirely safe; the NAS’s own software or firmware; or with the disks themselves (failed member drive, or RAID array no longer meeting minimum disk requirements). They are best evaluated in that order, ranging from non-harmful to potentially disastrous.
First, check your network. Network issues are the most common source of NAS problems, and they’re also generally the least worrying. Are other devices seeing the NAS on the network? Is there something wrong with your connection to the NAS? Check to see if you can get into the NAS from its IP address versus its name. Also, verify the NAS has both good cabling going to the NAS’s network port and a good spot on the switch that it’s plugged into. And lastly, please double-check that the NAS is getting power and all of its lights are working normally. If you can ping the NAS and power is being supplied and it will not display your shared directories, then the NAS’ issues could be related to either permissions/protocol (e.g. an SMB version mismatch), and therefore the NAS is probably fine. So if someone else can access the NAS and you can’t, then the issue is almost certainly with your system and not the NAS, so there is no reason for concern about losing data.
If everything looks good on the network side and your NAS is still refusing to provide access to your files then your NAS is down. Usually, some sort of error message or indication via the status lights will give you some idea of what type of failure occurred. For example, if your NAS comes up indicating one or more volumes have failed/degraded, then you’re looking at a hard drive problem. On the flip side, if your NAS won’t even start-up/boot properly then it may be a firmware problem. In either case, once again, your data is usually still stored on the individual drives; it’s just that the NAS can no longer make those available. At this point, what you don’t do matters: the main thing to keep away from is “repair” or “rebuild” options. These types of options will allow you to repair things in such a manner that you can irreparably ruin things that were otherwise perfectly recoverable.
A failure in one of your disks and the loss of an available disk for use within the NAS array will cause degradation. Normally you would want to replace the failed disk and allow the NAS to rebuild. However if there was another weak disk present within the NAS array a rebuild could create undue amounts of pressure upon each of the remaining disks, potentially writing over the original data required to restore the array, which is where data associated with NAS arrays are most likely to be irrecoverably lost. Similarly reinitialising or “repairing” a volume has the same potential for data loss. For a failed NAS, the safe steps are: shut off the NAS, image all disks read only and rebuild the array offline using the copied images. Details for rebuilding a RAID array can be found at our guide titled what to do when a RAID won’t rebuild. We can recover data from a NAS or RAID array starting at £500 +VAT. Please send us your failed NAS unit or all individual disks labelled by bay number.
There are three different possibilities: your network is malfunctioning (you may have recently changed your IP address, changed your DNS configuration or altered your router settings, you may need to swap cables or alter permission configurations), the NAS software/firmware is faulty, or the NAS disk itself has failed or the RAID array has degraded. Network related issues are normally the most common and do not put your data at risk. Issues associated with either your disks/RAID array are dangerous. First investigate your network and then test your NAS.
Check that other users can connect to the NAS (check it via its IP address rather than its name) and check to see if it is receiving power and displaying the correct status LEDs. If someone else can access the NAS but you can’t, this means there’s an issue somewhere along your network or permissions setup. In this case, no data will be lost. If nobody can connect to the NAS, or the status LEDs are showing a warning light, then the most likely cause for this problem is with the NAS hardware or its hard drives.
Don’t rush into rebuilding it. If another disk is also failing, rebuilding onto a different one may place considerable stress on the RAID array and erase the data required to recreate it, which is typically how NAS data is lost. Simply switch off the NAS unit, avoid trying to reset/initialise it, and have it recovered by creating read-only images of each drive and then rebuilding the array offline.
Normally, yes. The NAS uses the individual disks to store its data, therefore even if the NAS unit is dead, or its firmware has ceased functioning, we can still recover the RAID array using read-only images of each drive. Please ship the complete unit or all of the drives, labelled in bay order. We offer a free diagnostic on all NAS & RAID recovery projects, which start from £500 + VAT.
Ship either the complete NAS unit, or the disks themselves with labels detailing their bay order. This is because we can only restore the RAID array with all disks present and in bay order. Please do not mix up the disks or attempt to determine their order yourself. Additionally, do not let the NAS rebuild onto a new disk first. As well as our free diagnostic service prior to any chargeable works, we provide a fixed price quotation.
If a disk on the NAS has failed or the array has dropped, power the NAS down and send the unit or its drives in bay order. We will reconstruct the array offline using read-only images, with a free diagnostic and a fixed-price quotation first.