A NAS you suddenly can’t reach is alarming — it’s often where the important shared files and backups live. But “not accessible” covers a wide range, from a simple network hiccup to a failed disk to a collapsed RAID array, and the cause decides what’s safe to do next. Here’s how to tell which you’re facing, and how to recover the data if the NAS itself has failed.
Sometimes the NAS is fine and the network is the problem. Sometimes a disk has failed. Sometimes the RAID array has dropped. Work out which before you touch anything — because the wrong recovery step can lose the lot.
A NAS is really a small computer with its own operating system, network connection, and a set of disks in a RAID array — and a problem with any of those can make it unreachable. The fault might be purely on the network (a changed IP address, a DNS or router issue, a bad cable, or permissions), in which case the data is completely safe. It might be the NAS’s own software or firmware. Or it might be the disks — a failed member drive, or a RAID array that’s dropped below the number of working disks it needs. Because these range from harmless to serious, it’s worth checking them in that order.
Start with the network, because it’s the commonest cause and the least worrying. Can other devices see the NAS, or is it just yours? Try reaching it by its IP address rather than its name, check its network cable and switch port, and confirm it still has power and its status lights look normal. A NAS that’s pingable and powered but not showing shared folders may be a permissions or protocol issue (an SMB version mismatch, say) rather than a fault at all. If other people can access it and you can’t, the problem is almost certainly at your end, not the NAS — and no data is at risk.
If the network checks out but the NAS still won’t serve its files, the trouble is inside the unit. The status lights or admin interface often tell the story: a warning about a failed or degraded volume points to a disk problem, while a unit that won’t boot at all may have a firmware fault. Either way, the data usually still lives on the disks — it’s the NAS’s ability to present it that’s broken. What matters now is what you don’t do: this is the moment people reach for “repair” or “rebuild” options that can make a recoverable situation unrecoverable.
If a disk has failed and the array is degraded, the instinct is to drop in a new disk and let the NAS rebuild — and on a healthy array that’s normal. But if any other disk is also weak, a rebuild hammers every drive and can overwrite the data needed to reconstruct the array, which is how NAS data is most often lost for good. The same goes for re-initialising or “repairing” a volume. The safe route with a failed NAS is to power it down and recover it properly: every disk is imaged read-only and the array rebuilt offline from those copies — the approach in our guide on what to do when a RAID won’t rebuild. Send the whole unit, or all the drives labelled in bay order; NAS and RAID recovery is from £500 +VAT.
It could be one of three things: a network problem (a changed IP, DNS or router issue, a bad cable, or permissions), the NAS own software or firmware, or the disks, a failed drive or a degraded RAID array. Network problems are the commonest and leave your data safe; disk and array problems are serious. Check the network first, then the unit.
Check whether other devices can reach the NAS or only yours cannot, try its IP address rather than its name, and confirm it has power and normal status lights. If others can access it and you cannot, it is a network or permissions issue at your end and no data is at risk. If nobody can reach it, or the lights show a warning, the fault is likely in the unit or its disks.
Do not rush to rebuild it. If another disk is also weak, rebuilding onto a replacement can stress the array and overwrite the data needed to reconstruct it, which is the most common way NAS data is lost. Power the unit down, do not re-initialise it, and get it recovered by imaging every disk read-only and rebuilding the array offline.
Usually, yes. The data lives on the disks, so even if the NAS unit is dead or its firmware has failed, the array can be rebuilt offline from read-only images of the drives. Send the whole unit, or all the drives labelled with their bay order. NAS and RAID recovery starts from 500 pounds plus VAT after a free diagnostic.
Send the whole NAS unit, or all of its drives labelled with their bay order, the array can only be rebuilt with every member disk present and in the right order. Do not swap disks around or try to guess the order, and do not let the NAS rebuild onto a new disk first. A free diagnostic and fixed quote come before any chargeable work.
If a disk has failed or the array has dropped, power the NAS down and send the unit or its bay-ordered drives in. We rebuild the array offline from read-only images — free diagnostic, fixed quote first.