NDR / Whatever it is saying now / Synology storage pool degraded

Storage Manager · Degraded · one drive down · the repair

Synology says the storage pool is degraded. Still readable, still recoverable, and one repair away from neither.

Degraded is the good news that sounds bad. Synology's own definition is that a storage pool becomes Degraded when one or more of its drives becomes defective, but the storage pool remains accessible; the redundancy is gone and the data is not. What happens next decides the job. The instinct is to fit a new drive and click Repair, which asks DSM to read every sector of every surviving drive to rebuild the missing one. On drives that have lived the same years in the same case, that is where the second failure is found, and Degraded becomes Crashed. Copy what matters, power down, and send the set. A degraded set is £500 + VAT upwards after the free look, fixed in writing, 5–10 days at the bench.

Free first lookOne fixed figure in writingNo data, no bill on most jobsReturn postage paid

Rather talk it through? An engineer answers the bench line
0800 6890668

Power it down. Label each drive with its bay number. Do not rebuild, repair, initialise, reinstall or reset. A rebuild reads every sector of every surviving drive, and on a set with a second weak member it finishes what the first failure began. Nothing on the drives gets worse while the unit is off.

Why the repair is the dangerous part.

A RAID 5 or SHR pool with one drive gone is a pool with no spare copies. Every read now depends on every remaining drive answering, and every remaining drive has been spinning beside the one that failed, for the same hours, in the same heat. Drives do not fail at random; they fail in batches, and a pool that has just lost one has usually got another close behind.

The repair is where that shows. To rebuild the missing drive, DSM reads every sector of every survivor, including the sectors nobody has touched since the pool was made and the ones a survivor has been quietly working around. A survivor that throws an unrecoverable read error part-way through drops out of the array, and with two members gone, a RAID 5 or single-parity SHR cannot continue. The repair stops, the pool reads Crashed, and the situation is now worse than it was, because the new drive is half-written and the survivor has been marked failed.

The bench does the same arithmetic without the risk. Every drive, including the one that failed, is imaged once, the weak ones slowly with their bad areas last, and the parity is run on the images, which cannot drop out. If the failed drive still reads at all, its stripes fill the gaps in any survivor that could not give them. A degraded pool that was powered down is one of the better jobs there is; the same pool after a stalled repair is a harder one.

What it says, and what it means.

Describe yours to us →

What you see	The usual reason	Where that leaves you
Degraded; volume readable	One member lost	Copy critical files; power down; send the set
Degraded; repair offered	DSM wants a new drive	Decline until the data is safe elsewhere
Repair at n per cent, then Crashed	A survivor's read errors	Every member imaged; parity run on the images
Degraded with a second drive showing warnings	The next failure, announced	Power down now
Degraded after a drive was pulled by mistake	DSM dropped the pulled drive	Do not reinsert and Repair; the event counts decide

From the box arriving to your files going back.

Work we have closed →

Logged the day it lands, and the first look costs nothing Free

A case number goes on the parcel and a number on every drive the day it is opened, and an engineer settles what has actually happened before anything spins. The unit is examined on its own; each drive is assessed on our own equipment, never in a NAS that will try to rebuild. Back to you come two things together: a straight note of what is liftable and what is not, plus one figure, fixed and written down. Accept it, or decline and owe us nothing.

Nothing to pay for lookingA single figure, put in writingNo rebuilds, no repairs, no resets

The unit, and the drives, apart

The box and the disks are two different jobs. The unit is tested separately, because a dead power supply, a failed board or a bricked boot flash leaves the drives untouched more often than not. Each drive is then read on the bench: the ones that answer at full speed, and the weak or failed ones in clean air where they need head work. On units that hold an encryption key or a layout of their own, the unit is part of the data and is kept with it.

Unit and disks assessed separatelyFailing members to the clean bench

Every member imaged, once

Nothing is worked on live and nothing is rebuilt on the originals. Every drive in the set is imaged sector by sector, the weak ones head by head with the bad areas last, and the SSD cache with them where there is one. From then on the originals are not touched again.

Every drive, including the cacheWeak areas last

The set put back together, from the images

Order, chunk size, parity rotation and the reshape point are read from the drives' own metadata and the array is reassembled in software: mdadm and LVM under SHR, X-RAID and QTS pools; a ZFS pool imported read-only; Drobo's BeyondRAID zones reconstructed. The file system, Btrfs, ext4, XFS or ZFS, is repaired on the virtual volume, and encrypted volumes are unlocked there with the key you supply. Never on the originals.

Rebuilt in software, from imagesThe file system repaired on the virtual volume

You see the file list before you pay

What was recovered is listed for you first, and only then does a bill exist. Approve the list and it is invoiced; turn it down and it is not — and where nothing has come back, most jobs carry no charge at all. Recovered data travels home on fresh media bought in for your job, with the postage at our end. Your case is not closed until you have opened the files on a machine of your own.

No charge until you accept the figureFresh media, supplied with the job5–10 days at the bench

From the bench

Copy what matters, not everything. A degraded pool reading every sector to serve a full copy is a degraded pool doing the repair by another name.
Do not fit the new drive. The repair starts the moment it is accepted, and cannot be paused once the survivor's bad sectors are found.
Auto Repair is not supported on SHR pools, Synology says, and manual repair on SHR reads every layer of every survivor.
If the repair already stalled, power down and leave it. The first-dropped drive still holds the stripes the repair never reached.

One job, followed all the way through.

UK · NDR-2026-0533JOB LOGGED ✓

A DS220+ in SHR whose owner fitted a new drive and watched the repair stop at 41 per cent

The survivor had bad sectors DSM had been working around for a year, and the repair found them. The owner powered down. Both original drives were imaged on the bench, the survivor slowly with its weak areas last, the dropped drive read for the stripes the survivor could not give, and the Btrfs volume mounted from the merged image. Everything came back.

100% of it recovered6 days here, and back by post

Illustrative example — replace with a genuine case

What helps, and what harms.

Do this much first

Copy the critical files once, while it still reads
Power it down
Write each bay number on its drive
Send every original drive and the unit; keep the new one

What sets us back

Fitting a replacement and clicking Repair
Copying the whole volume off through the degraded pool
Pulling drives to find the bad one
Running SMART extended tests, which read every sector too

Questions answered before you commit.

Synology says my pool is degraded. Is my data at risk?

It is readable now and recoverable in any case. What puts it at risk is the repair, which reads every sector of every survivor to rebuild the missing drive, on drives that have aged together. Copy what matters, power down, and send the set.

Should I replace the failed drive?

Not until the data is safe elsewhere. If every survivor is healthy the repair works; if any is weak, it stalls and the pool crashes. The bench does the same rebuild on images, where it cannot stall.

The repair stalled and now it says crashed. What now?

Power down and leave it. The drive that dropped first still holds the stripes the repair never reached, and the set is complete across the images.

What does it cost?

A set is £500 + VAT upwards after the free look, fixed in writing.

How long does it take?

5–10 days at the bench.

Where this usually leads.

Synology volume crashed →Two-bay NAS →Four-bay RAID 5 and 6 →Synology →

Nothing gets worse while it is powered down.

Looking at it is free. Back comes a list of what opened and what did not, together with a single price to finish, set down in writing while you are still free to say no. Until that list reaches you, leave the unit off and the drives in their bays.

0800 6890668

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