Your NAS has just sent an email or shown a red badge: a Seagate IronWolf or IronWolf Pro drive has a warning. It might come from IronWolf Health Management, from the NAS’s own SMART check, or from a scheduled scan that found bad sectors. Usually the NAS keeps working and the shares are still there, so it’s easy to put off. But a warning on one disk is the point where a NAS is most likely to go from “fine” to “lost volume”, and what you do in the next few hours matters more than what the warning says.
What the warning actually means
IronWolf drives are built for NAS use, and many NAS systems (Synology DSM, QNAP QTS/QuTS hero and others) can run Seagate’s IronWolf Health Management, which reads the drive’s own health data and reports whether it thinks the drive is healthy or needs attention. Separately, the NAS reads standard SMART values. The ones that matter most are:
- Reallocated sectors (SMART 5) – areas of the disk that failed and have been swapped for spare sectors. A small, stable number is not an emergency; a number that keeps rising is.
- Current pending sectors (SMART 197) – sectors the drive could not read and has not yet been able to replace. These are the ones that hurt during a rebuild.
- Offline uncorrectable (SMART 198) – sectors that failed during the drive’s own background scans.
Don’t be alarmed by the huge raw numbers Seagate drives show for “Raw read error rate” and “Seek error rate”. Seagate packs several counters into those fields, so the raw figure looks frightening on a perfectly good drive. Look at the reallocated and pending counts and at whether they are changing.
Why one warning is a bigger risk than it looks
In a RAID 1, RAID 5 or Synology SHR volume, the NAS can survive one failed disk. The problem is that the disks in a NAS were usually bought together, have run the same hours and have the same wear. When one drive starts reporting bad sectors, the others are often not far behind. If the warning drive fails and the NAS starts rebuilding onto a new disk, every sector of every remaining drive has to be read. A single unreadable area on another disk during that rebuild is the classic way a degraded volume becomes a crashed one. We see it regularly – it’s the scenario in our article on RAID 5 rebuilds that fail.
What to do first
- Back up the data that matters now, while the volume is healthy. Copy the most important shares to a separate USB drive or another device first, then the rest. Don’t wait for the replacement disk to arrive.
- Write down which drive is flagged. Note the bay number and the serial number shown in Storage Manager or Storage & Snapshots. Bay numbering is not always what you’d guess from the front panel.
- Check the other drives’ SMART data too. If a second disk also shows pending or reallocated sectors, treat the NAS as fragile and focus entirely on getting a copy off.
- Replace one disk at a time with a drive of the same or larger capacity, following your NAS’s replace-drive procedure. Let the repair finish completely before touching anything else.
- Check the warranty. Seagate’s warranty check on its website will tell you if the drive is covered, and whether your model came with any data recovery plan.
What not to do
- Don’t pull the wrong disk. Removing a healthy drive from a RAID 5 or SHR volume that already has a weak one can take the whole volume offline. Confirm the serial number before you remove anything.
- Don’t run extended scans over and over. A long SMART test reads the whole surface. Once is useful for diagnosis; repeating it on a degrading drive just adds wear before you’ve got a backup.
- Don’t swap more than one drive at once, or reinsert disks in different bays to “see what happens”.
- Don’t choose any option to create, initialise or reset a volume or storage pool if the NAS starts showing it as crashed. Those options are for new disks and will overwrite the existing layout.
- Don’t keep rebooting a NAS that hangs or drops a drive. Every restart re-reads the array and can mark another disk as failed.
If the volume is already degraded or crashed
If the NAS now says the volume or storage pool is degraded, crashed or read-only, stop writing to it. Copy off what you can if it is still accessible; if it isn’t, shut the NAS down cleanly and leave the disks in place and in order. A lab can image each drive individually, using specialist hardware to handle weak or damaged areas, and rebuild the RAID from the images rather than the original disks. That way the originals are never put through a risky rebuild. A drive that has started clicking or failed completely may need clean-room work before it can be imaged.
Our server and RAID data recovery service handles NAS units from all the main brands, and our hard drive data recovery team works on individual IronWolf drives that have failed outright.
Keeping it from happening again
- Let the NAS email you about drive health and scheduled scan results, and read them.
- Remember that RAID is not a backup. Keep a separate copy of the NAS on another device or in the cloud.
- Plan to replace disks before they are very old, ideally one at a time rather than all at once.
Talk to Data Doctor
If your IronWolf drive has a warning and you aren’t sure whether it’s safe to replace it, or the volume has already crashed, call Data Doctor on 020 7394 2529 for a free initial consultation. You can also bring the NAS and its disks to our clean-room lab at Unit 1, The Willows, 80 Willow Walk, London SE1 5SY.