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RAR / Whatever it is saying now / QNAP read-only, Synology crashed

RAID group degraded, set to read-only · Recover RAID · Storage pool Degraded · Crashed · Repair · md · LVM

QNAP read-only, Synology crashed: the array layer. What the two vendors say, what the md arrays underneath are doing, and where the NAS site takes over.

QNAP and Synology both run Linux mdadm under their storage, and both report its states in their own words. QNAP's log line is RAID group X is degraded, the RAID group has been set to read-only. Back up all the files immediately; its QTS documentation on recovering a RAID group with an error status says that RAID recovery only helps when disks are temporarily disconnected and then reconnected, that it does not help in the event of disk failure, and that each disk must be reinserted into its original drive bay. Synology's Knowledge Center says a storage pool becomes Degraded when one or more of its drives becomes defective but remains accessible because no data loss has occurred, and that when the status becomes Crashed you can no longer repair it by yourself. Underneath, in both cases, is an md array that has lost members past its parity or has too few current ones to assemble, and this page is about that layer and how it is reassembled from images. The unit itself, its dashboard, its Repair button and the reasons not to press it, are the NAS site's subject. A set of two to four members is £500 + VAT upwards after the free look, fixed in writing, 5–10 days at the bench.

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Rather talk it through? An engineer answers the bench line
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Do not press Repair or Recover RAID with a second drive weak, do not move the drives to another unit to see, and do not create a new pool on them. A repair reads every sector of the survivors; a new unit may offer to initialise; a new pool writes new superblocks. Power down, number the bays, and send every drive.

What each vendor's message means at the array layer, and what the drives hold.

QNAP. A QNAP storage pool is one or more RAID groups, each an mdadm array across a partition of every member, joined by LVM with thin volumes on top. When a member drops out past the point of comfort, QTS sets the RAID group read-only and logs it: RAID group X is degraded, the RAID group has been set to read-only. Back up all the files immediately. That is the moment to do exactly that. QNAP's Recover RAID function, per the QTS 5.0 documentation, only helps when disks are temporarily disconnected and then reconnected, does not help in the event of disk failure, and requires each disk to be reinserted into its original drive bay; it re-adds members whose superblocks still agree, and it does nothing for a member that has actually failed. A RAID group with an Error status is one that has lost members past its parity, and the md array underneath will not assemble.

Synology. A Synology storage pool is SHR or a classic RAID, built as mdadm arrays across partitions, with a small RAID 1 system partition on every drive and LVM joining the data arrays. The Knowledge Center's definitions are exact: Degraded means one or more drives has become defective but the pool remains accessible because no data loss has occurred; Crashed means the pool has lost more than its parity and you can no longer repair it by yourself. Repair, on a degraded pool, rebuilds onto a replacement by reading every survivor, and ReclaiMe quotes Synology's own caution that it does not guarantee data on crashed volumes will be rescued. Auto Repair, the Knowledge Center notes, is not supported on SHR pools.

At the array layer both are the same job. Every member is imaged; the mdadm superblocks are read from the images at their version's location, 1.2 on modern units; the current members are chosen by event count; each md array is assembled in software; the LVM group is joined from the md devices; and the ext4 or Btrfs volume is opened read-only on the result, with Btrfs snapshots read where they hold what the live volume lost. The unit, the bay order, the DSM or QTS version and what the dashboard offered are on the NAS site, and the same bench does both.

What it says, and what it means.

Describe yours to us →
What you see The usual reason Where that leaves you
QNAP: RAID group degraded, set to read-onlyOne member lost; writes stoppedCopy the files now; image the weak drive before Recover RAID or a rebuild
QNAP: RAID group ErrorPast the parity; md will not assembleEvery member imaged; assembled from images
QNAP: Recover RAID did nothingThe member has actually failedAs above; the function only reattaches
Synology: storage pool DegradedA drive defective; no data loss yetImage the weak drive before Repair
Synology: storage pool CrashedPast the parityPower down; every member imaged
Volume crashed; pool healthyThe file system on topA file-system job on the images

From the parcel arriving to your files going back.

Work we have closed →
01

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

A case number goes on the parcel and a number on every member the day it is opened, matched to the slot you wrote on it. Each member goes on the imager its interface needs, never on a controller, and its metadata is read before a sector is: the level, the order, the stripe size, the event counts that say which member is current and which dropped out first. An engineer settles what has happened to the set and how much of it can honestly be read back. 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 imports, no initialise
02

Every member imaged, including the one that failed first

Every drive in the set is imaged sector by sector, weak areas last, on hardware that controls every retry, with a map of what could not be read kept for each. Members with failed heads go to the clean bench first; that is the drive site's work and the same bench does it. The drive that dropped out first is imaged too, because it still holds every stripe written before it dropped, and a rebuild that stalled part-way never reached them.

Sector by sector, weak areas lastThe first-dropped member included
03

The geometry, from the metadata or from the parity

A QNAP or Synology set is assembled layer by layer from the images: each md array from its 1.2 superblocks with event counts choosing the current members; the LVM group from its metadata on the md devices; and the ext4 or Btrfs volume opened read-only on the logical volume, with snapshots read where they help. Nothing is written to any image.

Metadata first, parity secondOrder, stripe, rotation, offset
04

Assembled in software, and repaired on the virtual volume

The set is put together from the images in software, with nothing written to any of them: the current members in, the stale member used only to fill holes a survivor could not give. The file system is checked and repaired on a copy of the virtual volume, VMFS and CSV volumes opened and the virtual machines' disks extracted, databases repaired where they need it. The originals are not touched again.

Nothing written to the imagesVirtual machines and databases opened
05

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

  • Read-only on QNAP is the unit protecting you. Copy what matters while it still reads, then power down.
  • Recover RAID reattaches; it does not repair. QNAP's own documentation says it does not help in the event of disk failure.
  • Crashed on Synology means past the parity, and Synology's own words are that you can no longer repair it yourself. That is the moment to send it.
  • The unit is the NAS site's subject. This page is the md and LVM layers, and the same bench does both.

Tonight, in this order: stop writes and do not reboot repeatedly; press nothing the controller offers (F2, Import, Clear, Force online, Rebuild); photograph the screen and label the slots; export the log without changing state (PERC TTYLOG or storcli show all, an SSA diagnostic report, mdadm --examine on every member, zpool import with no flags, Get-VirtualDisk); power down and send every member, plus the controller if it was replaced or holds a key. The first-response page has the reasons.

One job, followed all the way through.

UK · RAR-2026-0624JOB LOGGED ✓

A QNAP TS-873 with a six-drive RAID 6 storage pool showing Error after two members failed and a third was reseated by the owner into the wrong bay, and Recover RAID that reported nothing to recover

All six drives came in with a note of which bay each had actually been in. The two failed members were imaged, one after a head swap; the reseated drive's superblock still recorded its true role, so the wrong bay was harmless on the bench. The md array was assembled from the images with event counts choosing the current members, the LVM thin pool joined from it, and the ext4 volumes opened read-only. The shares were copied out.

100% of the pool recovered8 days here, and back by post
Illustrative example — replace with a genuine case

What helps, and what harms.

Do this much first

  • Copy what still reads on a read-only QNAP
  • Power down and number the bays
  • Send every drive, and say the model and firmware version
  • Tell us whether Repair or Recover RAID was tried

What sets us back

  • Pressing Repair with a second drive weak
  • Moving drives between bays or units to see
  • Creating a new pool or volume on the drives
  • Running Recover RAID repeatedly on a failed member

Questions answered before you commit.

QNAP says my RAID group is degraded and read-only. What should I do?

Copy the files while it still reads, as the log line says; then power down and image the weak drive before Recover RAID or a rebuild. Read-only is QTS protecting the survivors.

Does QNAP's Recover RAID fix a failed disk?

No. QNAP's own documentation says it only helps when disks were temporarily disconnected and reconnected, and does not help in the event of disk failure.

Synology says the pool has crashed and cannot be repaired. Is the data gone?

Synology's words are that you can no longer repair it yourself. The members are usually imageable and the md arrays are assembled from images. Power down and send the drives.

Is this the page for my NAS?

For the array layer inside it. For the unit, the dashboard, the Repair button and what each status means, the NAS site covers it in full, and the same bench does both.

What does it cost?

£500 + VAT upwards for two to four members after the free look, fixed in writing; rack units from £1,250 + VAT.

Where this usually leads.

SHR and Synology RAID F1 →QNAP: the array layer →Synology: the array layer →mdadm: not enough devices, array inactive →

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 server off and the drives in their slots.

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