RAR / Every level and layout / JBOD, spanned and dynamic disks

JBOD · spanned · concatenated · dynamic disk · LDM · RAID-5 volume · Failed Redundancy · Foreign · Missing

JBOD, spanned volumes and Windows dynamic disks. No tolerance, a member's used size, and a database Windows keeps at the end of every disk.

A spanned or JBOD volume writes to one member until it is full and then moves to the next, with no striping and no parity. Losing a member loses only that member's range, but the file system's metadata may be on it, and every file that crossed the boundary is cut. Windows dynamic disks do the same as spanned volumes and add striped, mirrored and RAID-5 volumes managed by the Logical Disk Manager, which keeps its database in a reserved area at the end of every dynamic disk and reports its volumes as Healthy, Failed Redundancy, Failed, and its disks as Foreign or Missing when they move between machines or drop out. They arrive here from small servers, Windows desktops with a stack of drives and enclosures that concatenate their bays, and the bench needs the member order and each member's used size for a span, and the LDM database for a dynamic disk set. A set of two to four members 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 down. Label every slot before a drive comes out. Do not rebuild, do not force a drive online, do not import or clear a foreign configuration, do not initialise, and do not run chkdsk, fsck, zpool import -F or mdadm --create on the members. A rebuild reads every sector of every survivor and writes to the replacement; each of the commands writes to the drives. On images, all of them are reversible. On the originals, none of them is.

Spanned and dynamic disk symptoms, and what each means.

Not listed? Describe it on the form →

Failed Redundancy on a mirrored or RAID-5 volumeOne member gone; still readable. Image before repair.Do not delay

Failed on a spanned or striped volumeA member missing. Find it; do not delete the volume.Do not delay

Disks show as Foreign after a moveAnother machine's LDM database. Do not revert to basic.Do not delay

Disk shows MissingDropped out; the database on the others still describes it.Everyday job

Enclosure's JBOD volume gone after a bay failedThe concatenation is in the enclosure. Members imaged; the span rebuilt.Do not delay

Converted to basic diskThe LDM database was removed. The data is usually intact beneath.Do not delay

Packing it and posting it: power down, photograph the controller's screen or export its log, and write the slot number on each drive with a marker before it comes out of its carrier. Send every member of the set, including the one that failed first; it holds the stripes the rebuild never reached. Each drive travels in an anti-static bag inside its own padding, in a box with nothing able to move. Send the controller if it was replaced or holds an encryption key; otherwise it stays. Insure the parcel for what the data is worth, use a tracked service, and know that the posting address is not printed anywhere on this site; it arrives by email in reply to the form, with a booking sheet to print; the sheet inside the parcel is what matches it to your enquiry when it is opened. Or hand the sealed parcel in at the nearest of ten drop-off points, your name on the outside and the sheet inside; say where you are on the form and it comes by email. We pay the postage home either way. The whole of it is written up on the guide to packing and posting.

What it tolerates, what fails it, and what the bench has to find.

The LDM databaseWindows keeps about 1MB at the end of every dynamic disk describing every dynamic disk in the group, every volume and where each volume's extents fall. Damage on one disk is covered by the copies on the others; converting to basic removes it, and the extents stay where they were.

Order and used sizeA span writes member 1 to the end before touching member 2. A reconstruction needs the order and how much of each member was actually used, both in the LDM database or the enclosure's record, and both readable from the file system's own allocation map when the record is gone.

What a lost member takesOnly its own range, but if the file system's metadata was on it, the rest is a carving job; and every file that crossed a member boundary is cut at it. The free look says which files are whole.

Foreign and MissingDynamic disks moved to another Windows machine show as Foreign until imported, because the database names a group the new machine has not seen. Importing is usually safe with every disk present; reverting to basic is not.

What a reconstruction has to determine.

Describe yours to us →

Unknown	Where it is read from	What goes wrong when it is guessed
Member order	LDM database; enclosure record; file-system allocation map	Ranges concatenated wrongly
Used size per member	LDM extents; allocation map	Gaps or overlaps in the volume
Volume map (dynamic)	The LDM database at the end of each disk	Extents assigned to the wrong volume
File-system metadata position	The volume's own structures	A lost member's metadata leaves a carving job

From the parcel 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 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

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

The geometry, from the metadata or from the parity

Where the controller's metadata survives on the members, the order, stripe size, parity rotation and data offset are read from it. Where it was cleared or overwritten, they are recovered from the data: parity across the members at the same offset should XOR to zero on a consistent stripe, which confirms the level and finds the stale member; where parity lands says the rotation; entropy at stripe edges and the file system's own anchors give the stripe size, the order and the start.

Metadata first, parity secondOrder, stripe, rotation, offset

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

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

What arrives most often

Do not revert dynamic disks to basic. It removes the database that describes the volumes.
Import Foreign disks only with every disk present. A partial import brings up a volume with a member missing.
Say which bay failed on a JBOD enclosure. The enclosure's concatenation order is usually bay order, and it says which range is missing.
Files that crossed a boundary are cut there. The free look lists which are whole.

One job, followed all the way through.

UK · RAR-2026-0612JOB LOGGED ✓

A three-disk dynamic RAID-5 volume on Windows Server 2012 R2 holding a firm's archive, one disk failed, the volume Failed Redundancy for a year, then a second disk retired and the volume Failed

All three disks came in. The two failed disks were imaged, the year-old one directly and the recent one with its weak areas last; the LDM database was read from every image and the RAID-5 volume's extents, stripe and order taken from it. The volume was assembled from the healthy disk and the recent image, with the year-old image's stripes used only where the recent one could not read. The NTFS archive was copied out.

99.9% of the volume recovered7 days here, and back by post

Illustrative example — replace with a genuine case

What helps, and what harms.

Do this much first

Power down and label the disks
Send every member, including the one that failed a year ago
Tell us which volume type and which disk failed first
Say the Windows version

What sets us back

Reverting dynamic disks to basic
Importing Foreign disks with one missing
Deleting the failed volume to recreate it
Running chkdsk on a volume with a member missing

Questions answered before you commit.

My dynamic disks show as Foreign. Is the data gone?

No. They came from another Windows machine and the new one has not imported their database. With every disk present, importing is usually safe; reverting to basic is not.

One disk of my spanned volume failed. Is everything gone?

Only that disk's range, if it cannot be imaged, and it usually can. Files that crossed a boundary are cut at it; the rest are whole.

What is the LDM database?

Windows's record of every dynamic disk and volume, kept at the end of each dynamic disk. It is what the bench reads to map the volumes.

What does it cost?

£500 + VAT upwards for two to four members after the free look, fixed in writing.

How long does it take?

5–10 days at the bench.

Begin here if yours is doing the same thing.

Windows Storage Spaces and dynamic disks →RAID 0 →RAID 1 →Storage Spaces parity and mirror →

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. On most jobs an invoice only follows the data. Until that list reaches you, leave the server off and the drives in their slots.

0800 6890668

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